📦 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/rpc/RpcService.d.ts

@@ -0,0 +1,12 @@
+import { RpcProcedure } from './RpcProcedure';
+import { RpcMessagePort } from './RpcMessagePort';
+declare type RpcCallHandler<TPayload = any, TResult = any> = (payload: TPayload) => Promise<TResult>;
+interface RpcService {
+    readonly isOpen: () => boolean;
+    readonly open: () => Promise<void>;
+    readonly close: () => Promise<void>;
+    readonly addCallHandler: <TPayload, TResult>(procedure: RpcProcedure<TPayload, TResult>, handler: RpcCallHandler<TPayload, TResult>) => void;
+    readonly removeCallHandler: <TPayload, TResult>(procedure: RpcProcedure<TPayload, TResult>) => void;
+}
+declare function createRpcService(port: RpcMessagePort): RpcService;
+export { RpcService, createRpcService };