Fix missing feature field in project tasks API response

Resolves issue #282 by adding feature field to task dictionary in
TaskService.list_tasks() method. The project tasks API endpoint was
excluding the feature field while individual task API included it,
causing frontend to default to 'General' instead of showing custom
feature values.

Changes:
- Add feature field to task response in list_tasks method
- Maintains compatibility with existing API consumers
- All 212 tests pass with this change

python/src/server/services/projects/task_service.py

@@ -273,6 +273,7 @@ class TaskService:
                     "status": task["status"],
                     "assignee": task.get("assignee", "User"),
                     "task_order": task.get("task_order", 0),
+                    "feature": task.get("feature"),
                     "created_at": task["created_at"],
                     "updated_at": task["updated_at"],
                 })