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/series/aseries.py

@@ -0,0 +1,10 @@
+from sympy.core.sympify import sympify
+
+
+def aseries(expr, x=None, n=6, bound=0, hir=False):
+    """
+    See the docstring of Expr.aseries() for complete details of this wrapper.
+
+    """
+    expr = sympify(expr)
+    return expr.aseries(x, n, bound, hir)