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/tcp.pxd

@@ -0,0 +1,26 @@
+cdef class TCPServer(UVStreamServer):
+    cdef bind(self, system.sockaddr* addr, unsigned int flags=*)
+
+    @staticmethod
+    cdef TCPServer new(Loop loop, object protocol_factory, Server server,
+                       unsigned int flags,
+                       object backlog,
+                       object ssl,
+                       object ssl_handshake_timeout,
+                       object ssl_shutdown_timeout)
+
+
+cdef class TCPTransport(UVStream):
+    cdef:
+        bint __peername_set
+        bint __sockname_set
+        system.sockaddr_storage __peername
+        system.sockaddr_storage __sockname
+
+    cdef bind(self, system.sockaddr* addr, unsigned int flags=*)
+    cdef connect(self, system.sockaddr* addr)
+    cdef _set_nodelay(self)
+
+    @staticmethod
+    cdef TCPTransport new(Loop loop, object protocol, Server server,
+                          object waiter, object context)