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/exceptions.py

@@ -0,0 +1,18 @@
+"""
+fsspec user-defined exception classes
+"""
+
+import asyncio
+
+
+class BlocksizeMismatchError(ValueError):
+    """
+    Raised when a cached file is opened with a different blocksize than it was
+    written with
+    """
+
+
+class FSTimeoutError(asyncio.TimeoutError):
+    """
+    Raised when a fsspec function timed out occurs
+    """