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/sympy/utilities/pkgdata.py

@@ -0,0 +1,33 @@
+# This module is deprecated and will be removed.
+
+import sys
+import os
+from io import StringIO
+
+from sympy.utilities.decorator import deprecated
+
+
+@deprecated(
+    """
+    The sympy.utilities.pkgdata module and its get_resource function are
+    deprecated. Use the stdlib importlib.resources module instead.
+    """,
+    deprecated_since_version="1.12",
+    active_deprecations_target="pkgdata",
+)
+def get_resource(identifier, pkgname=__name__):
+
+    mod = sys.modules[pkgname]
+    fn = getattr(mod, '__file__', None)
+    if fn is None:
+        raise OSError("%r has no __file__!")
+    path = os.path.join(os.path.dirname(fn), identifier)
+    loader = getattr(mod, '__loader__', None)
+    if loader is not None:
+        try:
+            data = loader.get_data(path)
+        except (OSError, AttributeError):
+            pass
+        else:
+            return StringIO(data.decode('utf-8'))
+    return open(os.path.normpath(path), 'rb')