📦 添加虚拟环境和启动脚本

新增:
- backend/venv/ - Python 虚拟环境
- backend/start.sh - 启动脚本（使用虚拟环境）
- backend/requirements.txt - 依赖列表
- .gitignore - 忽略虚拟环境和缓存文件

说明:
- 每个项目使用独立虚拟环境
- 避免依赖冲突
- 启动脚本自动创建和激活虚拟环境

frontend/node_modules/workbox-window/utils/urlsMatch.d.ts

@@ -0,0 +1,11 @@
+import '../_version.js';
+/**
+ * Returns true if two URLs have the same `.href` property. The URLS can be
+ * relative, and if they are the current location href is used to resolve URLs.
+ *
+ * @private
+ * @param {string} url1
+ * @param {string} url2
+ * @return {boolean}
+ */
+export declare function urlsMatch(url1: string, url2: string): boolean;