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/matrices/exceptions.py

@@ -0,0 +1,26 @@
+"""
+Exceptions raised by the matrix module.
+"""
+
+
+class MatrixError(Exception):
+    pass
+
+
+class ShapeError(ValueError, MatrixError):
+    """Wrong matrix shape"""
+    pass
+
+
+class NonSquareMatrixError(ShapeError):
+    pass
+
+
+class NonInvertibleMatrixError(ValueError, MatrixError):
+    """The matrix in not invertible (division by multidimensional zero error)."""
+    pass
+
+
+class NonPositiveDefiniteMatrixError(ValueError, MatrixError):
+    """The matrix is not a positive-definite matrix."""
+    pass