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/utilities/timeutils.py

@@ -0,0 +1,75 @@
+"""Simple tools for timing functions' execution, when IPython is not available. """
+
+
+import timeit
+import math
+
+
+_scales = [1e0, 1e3, 1e6, 1e9]
+_units = ['s', 'ms', '\N{GREEK SMALL LETTER MU}s', 'ns']
+
+
+def timed(func, setup="pass", limit=None):
+    """Adaptively measure execution time of a function. """
+    timer = timeit.Timer(func, setup=setup)
+    repeat, number = 3, 1
+
+    for i in range(1, 10):
+        if timer.timeit(number) >= 0.2:
+            break
+        elif limit is not None and number >= limit:
+            break
+        else:
+            number *= 10
+
+    time = min(timer.repeat(repeat, number)) / number
+
+    if time > 0.0:
+        order = min(-int(math.floor(math.log10(time)) // 3), 3)
+    else:
+        order = 3
+
+    return (number, time, time*_scales[order], _units[order])
+
+
+# Code for doing inline timings of recursive algorithms.
+
+def __do_timings():
+    import os
+    res = os.getenv('SYMPY_TIMINGS', '')
+    res = [x.strip() for x in res.split(',')]
+    return set(res)
+
+_do_timings = __do_timings()
+_timestack = None
+
+
+def _print_timestack(stack, level=1):
+    print('-'*level, '%.2f %s%s' % (stack[2], stack[0], stack[3]))
+    for s in stack[1]:
+        _print_timestack(s, level + 1)
+
+
+def timethis(name):
+    def decorator(func):
+        if name not in _do_timings:
+            return func
+
+        def wrapper(*args, **kwargs):
+            from time import time
+            global _timestack
+            oldtimestack = _timestack
+            _timestack = [func.func_name, [], 0, args]
+            t1 = time()
+            r = func(*args, **kwargs)
+            t2 = time()
+            _timestack[2] = t2 - t1
+            if oldtimestack is not None:
+                oldtimestack[1].append(_timestack)
+                _timestack = oldtimestack
+            else:
+                _print_timestack(_timestack)
+                _timestack = None
+            return r
+        return wrapper
+    return decorator