fix(api): add response_class=Response to DELETE endpoint for 204 status

apps/api/app/api/routes/edit_plans.py

@@ -1,3 +1,4 @@
+from fastapi.responses import Response
 """剪辑计划管理 API — Phase 8 模板编排引擎.
 
 RESTful CRUD for EditPlan:
@@ -279,7 +280,7 @@ def update_plan(
     return _to_response(result)
 
 
-@router.delete("/{plan_id}", status_code=status.HTTP_204_NO_CONTENT)
+@router.delete("/{plan_id}", status_code=status.HTTP_204_NO_CONTENT, response_class=Response)
 def delete_plan(
     plan_id: str,
     db: Session = Depends(get_db_session),