fix: DELETE 204路由改用response_model=None并移除return None，彻底解决FastAPI断言错误

apps/api/app/api/routes/feature_flags.py

@@ -173,12 +173,12 @@ async def update_feature_flag(
         raise HTTPException(status_code=500, detail=f"Failed to update flag: {exc}")
 
 
-@router.delete("/{name}", status_code=status.HTTP_204_NO_CONTENT, response_class=Response)
+@router.delete("/{name}", status_code=status.HTTP_204_NO_CONTENT, response_model=None)
 async def delete_feature_flag(
     name: str,
     _: bool = Depends(_verify_internal_api_key),
     store: RedisFeatureFlagStore = Depends(_get_feature_flag_store),
-) -> None:
+) :
     """删除 Feature Flag。
 
     只允许删除 ALLOWED_FLAGS 列表中的 flag。
@@ -188,7 +188,7 @@ async def delete_feature_flag(
     try:
         deleted = store.delete(name)
         logger.info("Feature flag deleted: name=%s deleted=%s", name, deleted)
-        return None
+        pass
     except Exception as exc:
         logger.error("Failed to delete feature flag %s: %s", name, exc)
         raise HTTPException(status_code=500, detail=f"Failed to delete flag: {exc}")