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/starlette/concurrency.py

@@ -0,0 +1,63 @@
+from __future__ import annotations
+
+import functools
+import sys
+import warnings
+from collections.abc import AsyncIterator, Coroutine, Iterable, Iterator
+from typing import Callable, TypeVar
+
+import anyio.to_thread
+
+if sys.version_info >= (3, 10):  # pragma: no cover
+    from typing import ParamSpec
+else:  # pragma: no cover
+    from typing_extensions import ParamSpec
+
+P = ParamSpec("P")
+T = TypeVar("T")
+
+
+async def run_until_first_complete(*args: tuple[Callable, dict]) -> None:  # type: ignore[type-arg]
+    warnings.warn(
+        "run_until_first_complete is deprecated and will be removed in a future version.",
+        DeprecationWarning,
+    )
+
+    async with anyio.create_task_group() as task_group:
+
+        async def run(func: Callable[[], Coroutine]) -> None:  # type: ignore[type-arg]
+            await func()
+            task_group.cancel_scope.cancel()
+
+        for func, kwargs in args:
+            task_group.start_soon(run, functools.partial(func, **kwargs))
+
+
+async def run_in_threadpool(func: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> T:
+    func = functools.partial(func, *args, **kwargs)
+    return await anyio.to_thread.run_sync(func)
+
+
+class _StopIteration(Exception):
+    pass
+
+
+def _next(iterator: Iterator[T]) -> T:
+    # We can't raise `StopIteration` from within the threadpool iterator
+    # and catch it outside that context, so we coerce them into a different
+    # exception type.
+    try:
+        return next(iterator)
+    except StopIteration:
+        raise _StopIteration
+
+
+async def iterate_in_threadpool(
+    iterator: Iterable[T],
+) -> AsyncIterator[T]:
+    as_iterator = iter(iterator)
+    while True:
+        try:
+            yield await anyio.to_thread.run_sync(_next, as_iterator)
+        except _StopIteration:
+            break