chore: 添加虚拟环境到仓库

- 添加 backend_service/venv 虚拟环境
- 包含所有Python依赖包
- 注意：虚拟环境约393MB，包含12655个文件

backend_service/venv/lib/python3.13/site-packages/fastapi/exception_handlers.py

@@ -0,0 +1,34 @@
+from fastapi.encoders import jsonable_encoder
+from fastapi.exceptions import RequestValidationError, WebSocketRequestValidationError
+from fastapi.utils import is_body_allowed_for_status_code
+from fastapi.websockets import WebSocket
+from starlette.exceptions import HTTPException
+from starlette.requests import Request
+from starlette.responses import JSONResponse, Response
+from starlette.status import WS_1008_POLICY_VIOLATION
+
+
+async def http_exception_handler(request: Request, exc: HTTPException) -> Response:
+    headers = getattr(exc, "headers", None)
+    if not is_body_allowed_for_status_code(exc.status_code):
+        return Response(status_code=exc.status_code, headers=headers)
+    return JSONResponse(
+        {"detail": exc.detail}, status_code=exc.status_code, headers=headers
+    )
+
+
+async def request_validation_exception_handler(
+    request: Request, exc: RequestValidationError
+) -> JSONResponse:
+    return JSONResponse(
+        status_code=422,
+        content={"detail": jsonable_encoder(exc.errors())},
+    )
+
+
+async def websocket_request_validation_exception_handler(
+    websocket: WebSocket, exc: WebSocketRequestValidationError
+) -> None:
+    await websocket.close(
+        code=WS_1008_POLICY_VIOLATION, reason=jsonable_encoder(exc.errors())
+    )