📦 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/graphemer/lib/GraphemerHelper.d.ts

@@ -0,0 +1,32 @@
+declare class GraphemerHelper {
+    /**
+     * Check if the the character at the position {pos} of the string is surrogate
+     * @param str {string}
+     * @param pos {number}
+     * @returns {boolean}
+     */
+    static isSurrogate(str: string, pos: number): boolean;
+    /**
+     * The String.prototype.codePointAt polyfill
+     * Private function, gets a Unicode code point from a JavaScript UTF-16 string
+     * handling surrogate pairs appropriately
+     * @param str {string}
+     * @param idx {number}
+     * @returns {number}
+     */
+    static codePointAt(str: string, idx: number): number;
+    /**
+     * Private function, returns whether a break is allowed between the two given grapheme breaking classes
+     * Implemented the UAX #29 3.1.1 Grapheme Cluster Boundary Rules on extended grapheme clusters
+     * @param start {number}
+     * @param mid {Array<number>}
+     * @param end {number}
+     * @param startEmoji {number}
+     * @param midEmoji {Array<number>}
+     * @param endEmoji {number}
+     * @returns {number}
+     */
+    static shouldBreak(start: number, mid: number[], end: number, startEmoji: number, midEmoji: number[], endEmoji: number): number;
+}
+export default GraphemerHelper;
+//# sourceMappingURL=GraphemerHelper.d.ts.map