📦 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/@nodelib/fs.scandir/out/utils/fs.d.ts

@@ -0,0 +1,2 @@
+import type { Dirent, Stats } from '../types';
+export declare function createDirentFromStats(name: string, stats: Stats): Dirent;

frontend/node_modules/@nodelib/fs.scandir/out/utils/fs.js

@@ -0,0 +1,19 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.createDirentFromStats = void 0;
+class DirentFromStats {
+    constructor(name, stats) {
+        this.name = name;
+        this.isBlockDevice = stats.isBlockDevice.bind(stats);
+        this.isCharacterDevice = stats.isCharacterDevice.bind(stats);
+        this.isDirectory = stats.isDirectory.bind(stats);
+        this.isFIFO = stats.isFIFO.bind(stats);
+        this.isFile = stats.isFile.bind(stats);
+        this.isSocket = stats.isSocket.bind(stats);
+        this.isSymbolicLink = stats.isSymbolicLink.bind(stats);
+    }
+}
+function createDirentFromStats(name, stats) {
+    return new DirentFromStats(name, stats);
+}
+exports.createDirentFromStats = createDirentFromStats;

frontend/node_modules/@nodelib/fs.scandir/out/utils/index.d.ts

@@ -0,0 +1,2 @@
+import * as fs from './fs';
+export { fs };

frontend/node_modules/@nodelib/fs.scandir/out/utils/index.js

@@ -0,0 +1,5 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.fs = void 0;
+const fs = require("./fs");
+exports.fs = fs;