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/uvloop/handles/streamserver.pxd

@@ -0,0 +1,26 @@
+cdef class UVStreamServer(UVSocketHandle):
+    cdef:
+        int backlog
+        object ssl
+        object ssl_handshake_timeout
+        object ssl_shutdown_timeout
+        object protocol_factory
+        bint opened
+        Server _server
+
+    # All "inline" methods are final
+
+    cdef inline _init(self, Loop loop, object protocol_factory,
+                      Server server,
+                      object backlog,
+                      object ssl,
+                      object ssl_handshake_timeout,
+                      object ssl_shutdown_timeout)
+
+    cdef inline _mark_as_open(self)
+
+    cdef inline listen(self)
+    cdef inline _on_listen(self)
+
+    cdef UVStream _make_new_transport(self, object protocol, object waiter,
+                                      object context)