feat: Linear-style Task Board mit Drag&Drop

backend/Data/Entities.cs

@@ -19,7 +19,8 @@ public enum TaskState
     Backlog,
     InProgress,
     Blocked,
-    Done
+    Done,
+    Review
 }
 
 public static class TaskStateHelper
@@ -29,7 +30,8 @@ public static class TaskStateHelper
         [TaskState.Backlog] = "Backlog",
         [TaskState.InProgress] = "In progress",
         [TaskState.Blocked] = "Blocked",
-        [TaskState.Done] = "Done"
+        [TaskState.Done] = "Done",
+        [TaskState.Review] = "Review"
     };
 
     private static readonly Dictionary<string, TaskState> StringToState = new(StringComparer.OrdinalIgnoreCase)
@@ -37,11 +39,22 @@ public static class TaskStateHelper
         ["Backlog"] = TaskState.Backlog,
         ["In progress"] = TaskState.InProgress,
         ["Blocked"] = TaskState.Blocked,
-        ["Done"] = TaskState.Done
+        ["Done"] = TaskState.Done,
+        ["Review"] = TaskState.Review
+    };
+
+    /// <summary>Mapping from state string to display label.</summary>
+    private static readonly Dictionary<string, string> DisplayLabels = new(StringComparer.OrdinalIgnoreCase)
+    {
+        ["Backlog"] = "Offen",
+        ["In progress"] = "In Bearbeitung",
+        ["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"];
+    public static readonly string[] AllStates = ["Backlog", "In progress", "Blocked", "Done", "Review"];
 
     /// <summary>Convert a TaskState enum to its API string representation.</summary>
     public static string ToStateString(this TaskState state) => StateToString[state];
@@ -54,6 +67,10 @@ public static class TaskStateHelper
     public static bool IsValidState(string? state) =>
         !string.IsNullOrWhiteSpace(state) && StringToState.ContainsKey(state);
 
+    /// <summary>Returns the German display label for a state string.</summary>
+    public static string ToDisplayString(string? state) =>
+        state is not null && DisplayLabels.TryGetValue(state, out var label) ? label : state ?? "";
+
     public static bool IsInProgressOrBlocked(string? state) =>
         string.Equals(state, "In progress", StringComparison.OrdinalIgnoreCase)
         || string.Equals(state, "Blocked", StringComparison.OrdinalIgnoreCase);
@@ -61,6 +78,38 @@ public static class TaskStateHelper
     public static bool IsDoneOrBacklog(string? state) =>
         string.Equals(state, "Done", StringComparison.OrdinalIgnoreCase)
         || string.Equals(state, "Backlog", StringComparison.OrdinalIgnoreCase);
+
+    /// <summary>Group key for board responses (lowercased English state).</summary>
+    public static string BoardGroupKey(string? state)
+    {
+        if (string.IsNullOrWhiteSpace(state)) return "offen";
+        var lower = state.ToLowerInvariant();
+        return lower switch
+        {
+            "backlog" => "offen",
+            "in progress" => "inProgress",
+            "review" => "review",
+            "blocked" => "blocked",
+            "done" => "done",
+            _ => "offen"
+        };
+    }
+
+    /// <summary>Map a board group key back to the canonical state string.</summary>
+    public static string? BoardGroupToState(string? groupKey)
+    {
+        if (string.IsNullOrWhiteSpace(groupKey)) return null;
+        var lower = groupKey.ToLowerInvariant();
+        return lower switch
+        {
+            "offen" => "Backlog",
+            "inprogress" => "In progress",
+            "review" => "Review",
+            "blocked" => "Blocked",
+            "done" => "Done",
+            _ => null
+        };
+    }
 }
 
 public sealed class Project