📦 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/ForkTsCheckerWebpackPluginState.d.ts

@@ -0,0 +1,15 @@
+import { Tap } from 'tapable';
+import { FilesMatch, Report } from './reporter';
+import { Issue } from './issue';
+interface ForkTsCheckerWebpackPluginState {
+    issuesReportPromise: Promise<Report | undefined>;
+    dependenciesReportPromise: Promise<Report | undefined>;
+    issuesPromise: Promise<Issue[] | undefined>;
+    dependenciesPromise: Promise<FilesMatch | undefined>;
+    lastDependencies: FilesMatch | undefined;
+    watching: boolean;
+    initialized: boolean;
+    webpackDevServerDoneTap: Tap | undefined;
+}
+declare function createForkTsCheckerWebpackPluginState(): ForkTsCheckerWebpackPluginState;
+export { ForkTsCheckerWebpackPluginState, createForkTsCheckerWebpackPluginState };