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/numpy/_pytesttester.pyi

@@ -0,0 +1,18 @@
+from collections.abc import Iterable
+from typing import Literal as L
+
+__all__ = ["PytestTester"]
+
+class PytestTester:
+    module_name: str
+    def __init__(self, module_name: str) -> None: ...
+    def __call__(
+        self,
+        label: L["fast", "full"] = ...,
+        verbose: int = ...,
+        extra_argv: Iterable[str] | None = ...,
+        doctests: L[False] = ...,
+        coverage: bool = ...,
+        durations: int = ...,
+        tests: Iterable[str] | None = ...,
+    ) -> bool: ...