📦 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/fork-ts-checker-webpack-plugin/lib/watch/InclusiveNodeWatchFileSystem.d.ts

@@ -0,0 +1,15 @@
+import { ForkTsCheckerWebpackPluginState } from '../ForkTsCheckerWebpackPluginState';
+import { FSWatcher } from 'chokidar';
+import { Watcher, WatchFileSystem, WatchFileSystemOptions } from './WatchFileSystem';
+import { Compiler } from 'webpack';
+declare class InclusiveNodeWatchFileSystem implements WatchFileSystem {
+    private watchFileSystem;
+    private compiler;
+    private pluginState;
+    get watcher(): import("./WatchFileSystem").Watchpack;
+    readonly dirsWatchers: Map<string, FSWatcher | undefined>;
+    constructor(watchFileSystem: WatchFileSystem, compiler: Compiler, pluginState: ForkTsCheckerWebpackPluginState);
+    private paused;
+    watch(files: Iterable<string>, dirs: Iterable<string>, missing: Iterable<string>, startTime?: number, options?: Partial<WatchFileSystemOptions>, callback?: Function, callbackUndelayed?: Function): Watcher;
+}
+export { InclusiveNodeWatchFileSystem };