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/poll.pxd

@@ -0,0 +1,25 @@
+cdef class UVPoll(UVHandle):
+    cdef:
+        int fd
+        Handle reading_handle
+        Handle writing_handle
+
+    cdef _init(self, Loop loop, int fd)
+    cdef _close(self)
+
+    cdef inline _poll_start(self, int flags)
+    cdef inline _poll_stop(self)
+
+    cdef int is_active(self) noexcept
+
+    cdef is_reading(self)
+    cdef is_writing(self)
+
+    cdef start_reading(self, Handle callback)
+    cdef start_writing(self, Handle callback)
+    cdef stop_reading(self)
+    cdef stop_writing(self)
+    cdef stop(self)
+
+    @staticmethod
+    cdef UVPoll new(Loop loop, int fd)