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/socketio/tornado.py

@@ -0,0 +1,9 @@
+try:
+    from engineio.async_drivers.tornado import get_tornado_handler as \
+        get_engineio_handler
+except ImportError:  # pragma: no cover
+    get_engineio_handler = None
+
+
+def get_tornado_handler(socketio_server):  # pragma: no cover
+    return get_engineio_handler(socketio_server.eio)