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/pypika/clickhouse/condition.py

@@ -0,0 +1,11 @@
+from pypika.terms import Function
+
+
+class If(Function):
+    def __init__(self, *conditions, **kwargs):
+        super().__init__("if", *conditions, **kwargs)
+
+
+class MultiIf(Function):
+    def __init__(self, *conditions, **kwargs):
+        super().__init__("multiIf", *conditions, **kwargs)