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/requests/packages.py

@@ -0,0 +1,23 @@
+import sys
+
+from .compat import chardet
+
+# This code exists for backwards compatibility reasons.
+# I don't like it either. Just look the other way. :)
+
+for package in ("urllib3", "idna"):
+    locals()[package] = __import__(package)
+    # This traversal is apparently necessary such that the identities are
+    # preserved (requests.packages.urllib3.* is urllib3.*)
+    for mod in list(sys.modules):
+        if mod == package or mod.startswith(f"{package}."):
+            sys.modules[f"requests.packages.{mod}"] = sys.modules[mod]
+
+if chardet is not None:
+    target = chardet.__name__
+    for mod in list(sys.modules):
+        if mod == target or mod.startswith(f"{target}."):
+            imported_mod = sys.modules[mod]
+            sys.modules[f"requests.packages.{mod}"] = imported_mod
+            mod = mod.replace(target, "chardet")
+            sys.modules[f"requests.packages.{mod}"] = imported_mod