📦 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-cacheable-response/CacheableResponse.d.ts

@@ -0,0 +1,45 @@
+import './_version.js';
+export interface CacheableResponseOptions {
+    statuses?: number[];
+    headers?: {
+        [headerName: string]: string;
+    };
+}
+/**
+ * This class allows you to set up rules determining what
+ * status codes and/or headers need to be present in order for a
+ * [`Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response)
+ * to be considered cacheable.
+ *
+ * @memberof workbox-cacheable-response
+ */
+declare class CacheableResponse {
+    private readonly _statuses?;
+    private readonly _headers?;
+    /**
+     * To construct a new CacheableResponse instance you must provide at least
+     * one of the `config` properties.
+     *
+     * If both `statuses` and `headers` are specified, then both conditions must
+     * be met for the `Response` to be considered cacheable.
+     *
+     * @param {Object} config
+     * @param {Array<number>} [config.statuses] One or more status codes that a
+     * `Response` can have and be considered cacheable.
+     * @param {Object<string,string>} [config.headers] A mapping of header names
+     * and expected values that a `Response` can have and be considered cacheable.
+     * If multiple headers are provided, only one needs to be present.
+     */
+    constructor(config?: CacheableResponseOptions);
+    /**
+     * Checks a response to see whether it's cacheable or not, based on this
+     * object's configuration.
+     *
+     * @param {Response} response The response whose cacheability is being
+     * checked.
+     * @return {boolean} `true` if the `Response` is cacheable, and `false`
+     * otherwise.
+     */
+    isResponseCacheable(response: Response): boolean;
+}
+export { CacheableResponse };