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/h11/_version.py

@@ -0,0 +1,16 @@
+# This file must be kept very simple, because it is consumed from several
+# places -- it is imported by h11/__init__.py, execfile'd by setup.py, etc.
+
+# We use a simple scheme:
+#   1.0.0 -> 1.0.0+dev -> 1.1.0 -> 1.1.0+dev
+# where the +dev versions are never released into the wild, they're just what
+# we stick into the VCS in between releases.
+#
+# This is compatible with PEP 440:
+#   http://legacy.python.org/dev/peps/pep-0440/
+# via the use of the "local suffix" "+dev", which is disallowed on index
+# servers and causes 1.0.0+dev to sort after plain 1.0.0, which is what we
+# want. (Contrast with the special suffix 1.0.0.dev, which sorts *before*
+# 1.0.0.)
+
+__version__ = "0.16.0"