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/idle.pxd

@@ -0,0 +1,14 @@
+cdef class UVIdle(UVHandle):
+    cdef:
+        Handle h
+        bint running
+
+    # All "inline" methods are final
+
+    cdef _init(self, Loop loop, Handle h)
+
+    cdef inline stop(self)
+    cdef inline start(self)
+
+    @staticmethod
+    cdef UVIdle new(Loop loop, Handle h)