fix(db): register legacy task migrations

backend/Data/Migrations/20260618233002_AddActivityTaskReference.cs

@@ -1,37 +1,38 @@
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Migrations;
+using Nexus.Api.Data;
 
 #nullable disable
 
 namespace Nexus.Api.Migrations
 {
     /// <inheritdoc />
+    [DbContext(typeof(NexusDbContext))]
+    [Migration("20260618233002_AddActivityTaskReference")]
     public partial class AddActivityTaskReference : Migration
     {
         /// <inheritdoc />
         protected override void Up(MigrationBuilder migrationBuilder)
         {
-            migrationBuilder.AddColumn<Guid>(
-                name: "TaskId",
-                table: "Activity",
-                type: "uuid",
-                nullable: true);
+            migrationBuilder.Sql(
+                """
+                ALTER TABLE "Activity"
+                    ADD COLUMN IF NOT EXISTS "TaskId" uuid;
 
-            migrationBuilder.CreateIndex(
-                name: "IX_Activity_TaskId",
-                table: "Activity",
-                column: "TaskId");
+                CREATE INDEX IF NOT EXISTS "IX_Activity_TaskId"
+                    ON "Activity" ("TaskId");
+                """);
         }
 
         /// <inheritdoc />
         protected override void Down(MigrationBuilder migrationBuilder)
         {
-            migrationBuilder.DropIndex(
-                name: "IX_Activity_TaskId",
-                table: "Activity");
-
-            migrationBuilder.DropColumn(
-                name: "TaskId",
-                table: "Activity");
+            migrationBuilder.Sql(
+                """
+                DROP INDEX IF EXISTS "IX_Activity_TaskId";
+                ALTER TABLE "Activity"
+                    DROP COLUMN IF EXISTS "TaskId";
+                """);
         }
     }
 }