feat: Linear-style Task Board mit Drag&Drop

backend/Controllers/DashboardController.cs

@@ -158,6 +158,36 @@ public class DashboardController(IDashboardService dashboardService, ITaskServic
         };
     }
 
+    // ── Task Board Endpoints ──
+
+    [HttpGet("tasks/board")]
+    public async Task<TaskBoardResponse> GetBoard(CancellationToken ct)
+        => await taskService.GetBoardAsync(ct);
+
+    [HttpPatch("tasks/{id:guid}/move")]
+    public async Task<ActionResult<DashboardTaskDto>> MoveTask(
+        Guid id, [FromBody] MoveTaskRequest request, CancellationToken ct)
+    {
+        if (string.IsNullOrWhiteSpace(request.State))
+            return BadRequest(new { error = "State is required." });
+
+        var result = await taskService.MoveTaskAsync(id, request.State, ct);
+        return result.Outcome switch
+        {
+            TaskOperationOutcome.InvalidState => BadRequest(new { error = $"Unsupported state: '{request.State}'. Valid: {string.Join(", ", TaskStateHelper.AllStates)}" }),
+            TaskOperationOutcome.NotFound => NotFound(new { error = "Task not found." }),
+            _ => Ok(MapToDto(result.Task!))
+        };
+    }
+
+    [HttpPost("tasks/import-from-iris-todo")]
+    public async Task<ActionResult<ImportResultDto>> ImportFromIrisTodo(
+        [FromQuery] bool delete = false, CancellationToken ct = default)
+    {
+        var result = await taskService.ImportFromIrisTodoAsync(delete, ct);
+        return Ok(new ImportResultDto(result));
+    }
+
     private static DashboardTaskDto MapToDto(WorkTask t) => new(
         t.Id, t.Title, t.Detail, t.Source, t.State, t.Priority, t.AssignedTo, t.CreatedAt, t.UpdatedAt);
 }