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/testing/randtest.py

@@ -0,0 +1,19 @@
+"""
+.. deprecated:: 1.10
+
+   ``sympy.testing.randtest`` functions have been moved to
+   :mod:`sympy.core.random`.
+
+"""
+from sympy.utilities.exceptions import sympy_deprecation_warning
+
+sympy_deprecation_warning("The sympy.testing.randtest submodule is deprecated. Use sympy.core.random instead.",
+    deprecated_since_version="1.10",
+    active_deprecations_target="deprecated-sympy-testing-randtest")
+
+from sympy.core.random import (  # noqa:F401
+    random_complex_number,
+    verify_numerically,
+    test_derivative_numerically,
+    _randrange,
+    _randint)