feat: Phase 2 — Delegated State, Auth, Review-Gate, Notifications, Zombie-Reset

backend/Data/Entities.cs

@@ -18,6 +18,7 @@ public enum TaskState
 {
     Backlog,
     InProgress,
+    Delegated,
     Blocked,
     Done,
     Review
@@ -29,6 +30,7 @@ public static class TaskStateHelper
     {
         [TaskState.Backlog] = "Backlog",
         [TaskState.InProgress] = "In progress",
+        [TaskState.Delegated] = "Delegated",
         [TaskState.Blocked] = "Blocked",
         [TaskState.Done] = "Done",
         [TaskState.Review] = "Review"
@@ -38,6 +40,7 @@ public static class TaskStateHelper
     {
         ["Backlog"] = TaskState.Backlog,
         ["In progress"] = TaskState.InProgress,
+        ["Delegated"] = TaskState.Delegated,
         ["Blocked"] = TaskState.Blocked,
         ["Done"] = TaskState.Done,
         ["Review"] = TaskState.Review
@@ -48,13 +51,14 @@ public static class TaskStateHelper
     {
         ["Backlog"] = "Offen",
         ["In progress"] = "In Bearbeitung",
+        ["Delegated"] = "Delegiert",
         ["Review"] = "Review",
         ["Blocked"] = "Blockiert",
         ["Done"] = "Erledigt"
     };
 
     /// <summary>Valid task-state string values for API validation.</summary>
-    public static readonly string[] AllStates = ["Backlog", "In progress", "Blocked", "Done", "Review"];
+    public static readonly string[] AllStates = ["Backlog", "In progress", "Delegated", "Blocked", "Done", "Review"];
 
     /// <summary>Convert a TaskState enum to its API string representation.</summary>
     public static string ToStateString(this TaskState state) => StateToString[state];
@@ -88,6 +92,7 @@ public static class TaskStateHelper
         {
             "backlog" => "offen",
             "in progress" => "inProgress",
+            "delegated" => "delegated",
             "review" => "review",
             "blocked" => "blocked",
             "done" => "done",
@@ -104,6 +109,7 @@ public static class TaskStateHelper
         {
             "offen" => "Backlog",
             "inprogress" => "In progress",
+            "delegated" => "Delegated",
             "review" => "Review",
             "blocked" => "Blocked",
             "done" => "Done",
@@ -131,15 +137,32 @@ public sealed class WorkTask
     public string Priority { get; set; } = "Normal";
     public string Source { get; set; } = "bao";
     public string? AssignedTo { get; set; }
+    public Guid? ParentTaskId { get; set; }
+    public WorkTask? ParentTask { get; set; }
+    public ICollection<WorkTask> ChildTasks { get; set; } = new List<WorkTask>();
     public Guid? ProjectId { get; set; }
+    public DateTimeOffset? DueDate { get; set; }
     public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
     public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
 }
 
+public sealed class Notification
+{
+    public Guid Id { get; init; } = Guid.NewGuid();
+    public required string Type { get; set; }        // "task_assigned", "task_review", "task_blocked"
+    public required string Title { get; set; }        // "Neue Aufgabe: Memory-Index reparieren"
+    public string? Message { get; set; }              // Detailtext
+    public required string ForUser { get; set; }      // "bao" oder "iris"
+    public Guid? TaskId { get; set; }                 // Verknüpfte Task
+    public bool IsRead { get; set; } = false;
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
+
 public sealed class ActivityEvent
 {
     public long Id { get; init; }
     public required string Type { get; set; }
     public required string Message { get; set; }
+    public Guid? TaskId { get; set; }
     public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
 }

backend/Data/Migrations/20260618214335_AddNotifications.Designer.cs

@@ -0,0 +1,311 @@
+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Nexus.Api.Data;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    [DbContext(typeof(NexusDbContext))]
+    [Migration("20260618214335_AddNotifications")]
+    partial class AddNotifications
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.8")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("Nexus.Api.Data.ActivityEvent", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Message")
+                        .IsRequired()
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("CreatedAt");
+
+                    b.HasIndex("TaskId");
+
+                    b.ToTable("Activity");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("DisplayName")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<DateTimeOffset?>("LastLoginAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("NormalizedEmail")
+                        .IsRequired()
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Role")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("NormalizedEmail")
+                        .IsUnique();
+
+                    b.ToTable("Users");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.Notification", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("ForUser")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<bool>("IsRead")
+                        .HasColumnType("boolean");
+
+                    b.Property<string>("Message")
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(240)
+                        .HasColumnType("character varying(240)");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ForUser", "IsRead", "CreatedAt");
+
+                    b.ToTable("Notifications");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.Project", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(160)
+                        .HasColumnType("character varying(160)");
+
+                    b.Property<int>("Progress")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("Status")
+                        .HasColumnType("integer");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("Projects");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.RefreshToken", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid>("ConcurrencyStamp")
+                        .IsConcurrencyToken()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateTimeOffset>("ExpiresAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid>("FamilyId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("ReplacedByTokenHash")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<DateTimeOffset?>("RevokedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("TokenHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("uuid");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TokenHash")
+                        .IsUnique();
+
+                    b.HasIndex("UserId", "FamilyId");
+
+                    b.ToTable("RefreshTokens");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("AssignedTo")
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Detail")
+                        .HasMaxLength(2000)
+                        .HasColumnType("character varying(2000)");
+
+                    b.Property<DateTimeOffset?>("DueDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid?>("ParentTaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Priority")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<Guid?>("ProjectId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Source")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<string>("State")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(240)
+                        .HasColumnType("character varying(240)");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AssignedTo");
+
+                    b.HasIndex("ParentTaskId");
+
+                    b.HasIndex("Source");
+
+                    b.ToTable("Tasks");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.RefreshToken", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.NexusUser", "User")
+                        .WithMany("RefreshTokens")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.WorkTask", "ParentTask")
+                        .WithMany("ChildTasks")
+                        .HasForeignKey("ParentTaskId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.Navigation("ParentTask");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
+                {
+                    b.Navigation("RefreshTokens");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Navigation("ChildTasks");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

backend/Data/Migrations/20260618214335_AddNotifications.cs

@@ -0,0 +1,45 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddNotifications : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "Notifications",
+                columns: table => new
+                {
+                    Id = table.Column<Guid>(type: "uuid", nullable: false),
+                    Type = table.Column<string>(type: "character varying(60)", maxLength: 60, nullable: false),
+                    Title = table.Column<string>(type: "character varying(240)", maxLength: 240, nullable: false),
+                    Message = table.Column<string>(type: "character varying(1000)", maxLength: 1000, nullable: true),
+                    ForUser = table.Column<string>(type: "character varying(60)", maxLength: 60, nullable: false),
+                    TaskId = table.Column<Guid>(type: "uuid", nullable: true),
+                    IsRead = table.Column<bool>(type: "boolean", nullable: false),
+                    CreatedAt = table.Column<DateTimeOffset>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_Notifications", x => x.Id);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Notifications_ForUser_IsRead_CreatedAt",
+                table: "Notifications",
+                columns: new[] { "ForUser", "IsRead", "CreatedAt" });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "Notifications");
+        }
+    }
+}

backend/Data/Migrations/20260618233000_AddTaskParentChild.cs

@@ -0,0 +1,49 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddTaskParentChild : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<Guid>(
+                name: "ParentTaskId",
+                table: "Tasks",
+                type: "uuid",
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Tasks_ParentTaskId",
+                table: "Tasks",
+                column: "ParentTaskId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Tasks_Tasks_ParentTaskId",
+                table: "Tasks",
+                column: "ParentTaskId",
+                principalTable: "Tasks",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.SetNull);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Tasks_Tasks_ParentTaskId",
+                table: "Tasks");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Tasks_ParentTaskId",
+                table: "Tasks");
+
+            migrationBuilder.DropColumn(
+                name: "ParentTaskId",
+                table: "Tasks");
+        }
+    }
+}

backend/Data/Migrations/20260618233001_AddTaskDueDate.cs

@@ -0,0 +1,28 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddTaskDueDate : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<DateTimeOffset>(
+                name: "DueDate",
+                table: "Tasks",
+                type: "timestamp with time zone",
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "DueDate",
+                table: "Tasks");
+        }
+    }
+}

backend/Data/Migrations/20260618233002_AddActivityTaskReference.cs

@@ -0,0 +1,37 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddActivityTaskReference : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<Guid>(
+                name: "TaskId",
+                table: "Activity",
+                type: "uuid",
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Activity_TaskId",
+                table: "Activity",
+                column: "TaskId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_Activity_TaskId",
+                table: "Activity");
+
+            migrationBuilder.DropColumn(
+                name: "TaskId",
+                table: "Activity");
+        }
+    }
+}

backend/Data/Migrations/20260618233003_AddDelegatedState.Designer.cs

@@ -0,0 +1,270 @@
+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Nexus.Api.Data;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    [DbContext(typeof(NexusDbContext))]
+    [Migration("20260618233003_AddDelegatedState")]
+    partial class AddDelegatedState
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.8")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("Nexus.Api.Data.ActivityEvent", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Message")
+                        .IsRequired()
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("CreatedAt");
+
+                    b.HasIndex("TaskId");
+
+                    b.ToTable("Activity");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("DisplayName")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<DateTimeOffset?>("LastLoginAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("NormalizedEmail")
+                        .IsRequired()
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Role")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("NormalizedEmail")
+                        .IsUnique();
+
+                    b.ToTable("Users");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.Project", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(160)
+                        .HasColumnType("character varying(160)");
+
+                    b.Property<int>("Progress")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("Status")
+                        .HasColumnType("integer");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("Projects");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.RefreshToken", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid>("ConcurrencyStamp")
+                        .IsConcurrencyToken()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateTimeOffset>("ExpiresAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid>("FamilyId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("ReplacedByTokenHash")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<DateTimeOffset?>("RevokedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("TokenHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("uuid");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TokenHash")
+                        .IsUnique();
+
+                    b.HasIndex("UserId", "FamilyId");
+
+                    b.ToTable("RefreshTokens");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("AssignedTo")
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Detail")
+                        .HasMaxLength(2000)
+                        .HasColumnType("character varying(2000)");
+
+                    b.Property<DateTimeOffset?>("DueDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid?>("ParentTaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Priority")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<Guid?>("ProjectId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Source")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<string>("State")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(240)
+                        .HasColumnType("character varying(240)");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AssignedTo");
+
+                    b.HasIndex("ParentTaskId");
+
+                    b.HasIndex("Source");
+
+                    b.ToTable("Tasks");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.RefreshToken", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.NexusUser", "User")
+                        .WithMany("RefreshTokens")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.WorkTask", "ParentTask")
+                        .WithMany("ChildTasks")
+                        .HasForeignKey("ParentTaskId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.Navigation("ParentTask");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
+                {
+                    b.Navigation("RefreshTokens");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Navigation("ChildTasks");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

backend/Data/Migrations/20260618233003_AddDelegatedState.cs

@@ -0,0 +1,24 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddDelegatedState : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            // Delegated state is a pure code change to the TaskState enum and
+            // TaskStateHelper. No schema change required since the State column
+            // is already a free-form string column.
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            // No schema to revert.
+        }
+    }
+}

backend/Data/Migrations/NexusDbContextModelSnapshot.cs

@@ -38,12 +38,19 @@ namespace Nexus.Api.Migrations
                         .HasMaxLength(1000)
                         .HasColumnType("character varying(1000)");
 
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
                     b.Property<string>("Type")
                         .IsRequired()
                         .HasColumnType("text");
 
                     b.HasKey("Id");
 
+                    b.HasIndex("CreatedAt");
+
+                    b.HasIndex("TaskId");
+
                     b.ToTable("Activity");
                 });
 
@@ -93,6 +100,47 @@ namespace Nexus.Api.Migrations
                     b.ToTable("Users");
                 });
 
+            modelBuilder.Entity("Nexus.Api.Data.Notification", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("ForUser")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<bool>("IsRead")
+                        .HasColumnType("boolean");
+
+                    b.Property<string>("Message")
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(240)
+                        .HasColumnType("character varying(240)");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ForUser", "IsRead", "CreatedAt");
+
+                    b.ToTable("Notifications");
+                });
+
             modelBuilder.Entity("Nexus.Api.Data.Project", b =>
                 {
                     b.Property<Guid>("Id")
@@ -183,6 +231,12 @@ namespace Nexus.Api.Migrations
                         .HasMaxLength(2000)
                         .HasColumnType("character varying(2000)");
 
+                    b.Property<DateTimeOffset?>("DueDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid?>("ParentTaskId")
+                        .HasColumnType("uuid");
+
                     b.Property<string>("Priority")
                         .IsRequired()
                         .HasColumnType("text");
@@ -211,6 +265,8 @@ namespace Nexus.Api.Migrations
 
                     b.HasIndex("AssignedTo");
 
+                    b.HasIndex("ParentTaskId");
+
                     b.HasIndex("Source");
 
                     b.ToTable("Tasks");
@@ -227,10 +283,25 @@ namespace Nexus.Api.Migrations
                     b.Navigation("User");
                 });
 
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.WorkTask", "ParentTask")
+                        .WithMany("ChildTasks")
+                        .HasForeignKey("ParentTaskId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.Navigation("ParentTask");
+                });
+
             modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
                 {
                     b.Navigation("RefreshTokens");
                 });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Navigation("ChildTasks");
+                });
 #pragma warning restore 612, 618
         }
     }

backend/Data/NexusDbContext.cs

@@ -6,6 +6,7 @@ public sealed class NexusDbContext(DbContextOptions<NexusDbContext> options) : D
 {
     public DbSet<Project> Projects => Set<Project>();
     public DbSet<WorkTask> Tasks => Set<WorkTask>();
+    public DbSet<Notification> Notifications => Set<Notification>();
     public DbSet<ActivityEvent> Activity => Set<ActivityEvent>();
     public DbSet<NexusUser> Users => Set<NexusUser>();
     public DbSet<RefreshToken> RefreshTokens => Set<RefreshToken>();
@@ -21,8 +22,25 @@ public sealed class NexusDbContext(DbContextOptions<NexusDbContext> options) : D
             entity.Property(x => x.AssignedTo).HasMaxLength(60);
             entity.HasIndex(x => x.Source);
             entity.HasIndex(x => x.AssignedTo);
+            entity.HasOne(x => x.ParentTask)
+                  .WithMany(x => x.ChildTasks)
+                  .HasForeignKey(x => x.ParentTaskId)
+                  .OnDelete(DeleteBehavior.SetNull);
+        });
+        modelBuilder.Entity<Notification>(entity =>
+        {
+            entity.Property(x => x.Title).HasMaxLength(240);
+            entity.Property(x => x.Message).HasMaxLength(1000);
+            entity.Property(x => x.Type).HasMaxLength(60);
+            entity.Property(x => x.ForUser).HasMaxLength(60);
+            entity.HasIndex(x => new { x.ForUser, x.IsRead, x.CreatedAt });
+        });
+
+        modelBuilder.Entity<ActivityEvent>(entity =>
+        {
+            entity.Property(x => x.Message).HasMaxLength(1000);
+            entity.HasIndex(x => x.TaskId);
         });
-        modelBuilder.Entity<ActivityEvent>().Property(x => x.Message).HasMaxLength(1000);
         modelBuilder.Entity<NexusUser>().HasIndex(u => u.NormalizedEmail).IsUnique();
         modelBuilder.Entity<RefreshToken>().HasIndex(r => r.TokenHash).IsUnique();
         modelBuilder.Entity<RefreshToken>().HasIndex(r => new { r.UserId, r.FamilyId });