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/codegen/pyutils.py

@@ -0,0 +1,24 @@
+from sympy.printing.pycode import PythonCodePrinter
+
+""" This module collects utilities for rendering Python code. """
+
+
+def render_as_module(content, standard='python3'):
+    """Renders Python code as a module (with the required imports).
+
+    Parameters
+    ==========
+
+    standard :
+        See the parameter ``standard`` in
+        :meth:`sympy.printing.pycode.pycode`
+    """
+
+    printer = PythonCodePrinter({'standard':standard})
+    pystr = printer.doprint(content)
+    if printer._settings['fully_qualified_modules']:
+        module_imports_str = '\n'.join('import %s' % k for k in printer.module_imports)
+    else:
+        module_imports_str = '\n'.join(['from %s import %s' % (k, ', '.join(v)) for
+                                        k, v in printer.module_imports.items()])
+    return module_imports_str + '\n\n' + pystr