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/rich/_timer.py

@@ -0,0 +1,19 @@
+"""
+Timer context manager, only used in debug.
+
+"""
+
+from time import time
+
+import contextlib
+from typing import Generator
+
+
+@contextlib.contextmanager
+def timer(subject: str = "time") -> Generator[None, None, None]:
+    """print the elapsed time. (only used in debugging)"""
+    start = time()
+    yield
+    elapsed = time() - start
+    elapsed_ms = elapsed * 1000
+    print(f"{subject} elapsed {elapsed_ms:.1f}ms")