fix(api): 修复edit_plans.py中DELETE接口204响应体问题

添加response_class=Response，确保204响应无body。

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

@@ -25,7 +25,7 @@ from app.auth import AuthenticatedUser, get_current_user
 from app.dependencies import get_db_session, get_project_repository
 from app.schemas.generation_task import GenerationTaskResponse
 from app.services import EditPlanService
-from fastapi import APIRouter, Depends, HTTPException, Query, status
+from fastapi import APIRouter, Depends, HTTPException, Query, status, Response
 from pydantic import BaseModel, Field
 from sqlalchemy.orm import Session
 
@@ -421,7 +421,7 @@ def update_plan(
     return _to_response(result)
 
 
-@router.delete("/{plan_id}", status_code=status.HTTP_204_NO_CONTENT, response_model=None)
+@router.delete("/{plan_id}", status_code=status.HTTP_204_NO_CONTENT, response_model=None, response_class=Response)
 def delete_plan(
     plan_id: str,
     db: Session = Depends(get_db_session),