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/fsspec/dircache.py

@@ -0,0 +1,98 @@
+import time
+from collections.abc import MutableMapping
+from functools import lru_cache
+
+
+class DirCache(MutableMapping):
+    """
+    Caching of directory listings, in a structure like::
+
+        {"path0": [
+            {"name": "path0/file0",
+             "size": 123,
+             "type": "file",
+             ...
+            },
+            {"name": "path0/file1",
+            },
+            ...
+            ],
+         "path1": [...]
+        }
+
+    Parameters to this class control listing expiry or indeed turn
+    caching off
+    """
+
+    def __init__(
+        self,
+        use_listings_cache=True,
+        listings_expiry_time=None,
+        max_paths=None,
+        **kwargs,
+    ):
+        """
+
+        Parameters
+        ----------
+        use_listings_cache: bool
+            If False, this cache never returns items, but always reports KeyError,
+            and setting items has no effect
+        listings_expiry_time: int or float (optional)
+            Time in seconds that a listing is considered valid. If None,
+            listings do not expire.
+        max_paths: int (optional)
+            The number of most recent listings that are considered valid; 'recent'
+            refers to when the entry was set.
+        """
+        self._cache = {}
+        self._times = {}
+        if max_paths:
+            self._q = lru_cache(max_paths + 1)(lambda key: self._cache.pop(key, None))
+        self.use_listings_cache = use_listings_cache
+        self.listings_expiry_time = listings_expiry_time
+        self.max_paths = max_paths
+
+    def __getitem__(self, item):
+        if self.listings_expiry_time is not None:
+            if self._times.get(item, 0) - time.time() < -self.listings_expiry_time:
+                del self._cache[item]
+        if self.max_paths:
+            self._q(item)
+        return self._cache[item]  # maybe raises KeyError
+
+    def clear(self):
+        self._cache.clear()
+
+    def __len__(self):
+        return len(self._cache)
+
+    def __contains__(self, item):
+        try:
+            self[item]
+            return True
+        except KeyError:
+            return False
+
+    def __setitem__(self, key, value):
+        if not self.use_listings_cache:
+            return
+        if self.max_paths:
+            self._q(key)
+        self._cache[key] = value
+        if self.listings_expiry_time is not None:
+            self._times[key] = time.time()
+
+    def __delitem__(self, key):
+        del self._cache[key]
+
+    def __iter__(self):
+        entries = list(self._cache)
+
+        return (k for k in entries if k in self)
+
+    def __reduce__(self):
+        return (
+            DirCache,
+            (self.use_listings_cache, self.listings_expiry_time, self.max_paths),
+        )