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/websockets/asyncio/compatibility.py

@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+import sys
+
+
+__all__ = ["TimeoutError", "aiter", "anext", "asyncio_timeout", "asyncio_timeout_at"]
+
+
+if sys.version_info[:2] >= (3, 11):
+    TimeoutError = TimeoutError
+    aiter = aiter
+    anext = anext
+    from asyncio import (
+        timeout as asyncio_timeout,  # noqa: F401
+        timeout_at as asyncio_timeout_at,  # noqa: F401
+    )
+
+else:  # Python < 3.11
+    from asyncio import TimeoutError
+
+    def aiter(async_iterable):
+        return type(async_iterable).__aiter__(async_iterable)
+
+    async def anext(async_iterator):
+        return await type(async_iterator).__anext__(async_iterator)
+
+    from .async_timeout import (
+        timeout as asyncio_timeout,  # noqa: F401
+        timeout_at as asyncio_timeout_at,  # noqa: F401
+    )