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/polys/polyconfig.py

@@ -0,0 +1,67 @@
+"""Configuration utilities for polynomial manipulation algorithms. """
+
+
+from contextlib import contextmanager
+
+_default_config = {
+    'USE_COLLINS_RESULTANT':      False,
+    'USE_SIMPLIFY_GCD':           True,
+    'USE_HEU_GCD':                True,
+
+    'USE_IRREDUCIBLE_IN_FACTOR':  False,
+    'USE_CYCLOTOMIC_FACTOR':      True,
+
+    'EEZ_RESTART_IF_NEEDED':      True,
+    'EEZ_NUMBER_OF_CONFIGS':      3,
+    'EEZ_NUMBER_OF_TRIES':        5,
+    'EEZ_MODULUS_STEP':           2,
+
+    'GF_IRRED_METHOD':            'rabin',
+    'GF_FACTOR_METHOD':           'zassenhaus',
+
+    'GROEBNER':                   'buchberger',
+}
+
+_current_config = {}
+
+@contextmanager
+def using(**kwargs):
+    for k, v in kwargs.items():
+        setup(k, v)
+
+    yield
+
+    for k in kwargs.keys():
+        setup(k)
+
+def setup(key, value=None):
+    """Assign a value to (or reset) a configuration item. """
+    key = key.upper()
+
+    if value is not None:
+        _current_config[key] = value
+    else:
+        _current_config[key] = _default_config[key]
+
+
+def query(key):
+    """Ask for a value of the given configuration item. """
+    return _current_config.get(key.upper(), None)
+
+
+def configure():
+    """Initialized configuration of polys module. """
+    from os import getenv
+
+    for key, default in _default_config.items():
+        value = getenv('SYMPY_' + key)
+
+        if value is not None:
+            try:
+                _current_config[key] = eval(value)
+            except NameError:
+                _current_config[key] = value
+        else:
+            _current_config[key] = default
+
+configure()