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/logic/utilities/__init__.py

@@ -0,0 +1,3 @@
+from .dimacs import load_file
+
+__all__ = ['load_file']

backend_service/venv/lib/python3.13/site-packages/sympy/logic/utilities/dimacs.py

@@ -0,0 +1,69 @@
+"""For reading in DIMACS file format
+
+www.cs.ubc.ca/~hoos/SATLIB/Benchmarks/SAT/satformat.ps
+
+"""
+
+from sympy.core import Symbol
+from sympy.logic.boolalg import And, Or
+import re
+from pathlib import Path
+
+
+def load(s):
+    """Loads a boolean expression from a string.
+
+    Examples
+    ========
+
+    >>> from sympy.logic.utilities.dimacs import load
+    >>> load('1')
+    cnf_1
+    >>> load('1 2')
+    cnf_1 | cnf_2
+    >>> load('1 \\n 2')
+    cnf_1 & cnf_2
+    >>> load('1 2 \\n 3')
+    cnf_3 & (cnf_1 | cnf_2)
+    """
+    clauses = []
+
+    lines = s.split('\n')
+
+    pComment = re.compile(r'c.*')
+    pStats = re.compile(r'p\s*cnf\s*(\d*)\s*(\d*)')
+
+    while len(lines) > 0:
+        line = lines.pop(0)
+
+        # Only deal with lines that aren't comments
+        if not pComment.match(line):
+            m = pStats.match(line)
+
+            if not m:
+                nums = line.rstrip('\n').split(' ')
+                list = []
+                for lit in nums:
+                    if lit != '':
+                        if int(lit) == 0:
+                            continue
+                        num = abs(int(lit))
+                        sign = True
+                        if int(lit) < 0:
+                            sign = False
+
+                        if sign:
+                            list.append(Symbol("cnf_%s" % num))
+                        else:
+                            list.append(~Symbol("cnf_%s" % num))
+
+                if len(list) > 0:
+                    clauses.append(Or(*list))
+
+    return And(*clauses)
+
+
+def load_file(location):
+    """Loads a boolean expression from a file."""
+    s = Path(location).read_text()
+    return load(s)