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/multidict/_compat.py

@@ -0,0 +1,15 @@
+import os
+import platform
+
+NO_EXTENSIONS = bool(os.environ.get("MULTIDICT_NO_EXTENSIONS"))
+
+PYPY = platform.python_implementation() == "PyPy"
+
+USE_EXTENSIONS = not NO_EXTENSIONS and not PYPY
+
+if USE_EXTENSIONS:
+    try:
+        from . import _multidict  # type: ignore[attr-defined]  # noqa: F401
+    except ImportError:  # pragma: no cover
+        # FIXME: Refactor for coverage. See #837.
+        USE_EXTENSIONS = False