fix: 修复 express 导入方式

- 使用 ES6 默认导入替代 namespace 导入
- 修复 "express is not a function" 错误

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/index.ts

@@ -2,8 +2,8 @@ import { NestFactory } from '@nestjs/core';
 import { ExpressAdapter } from '@nestjs/platform-express';
 import { ValidationPipe } from '@nestjs/common';
 import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
-import * as express from 'express';
-import * as bodyParser from 'body-parser';
+import express from 'express';
+import bodyParser from 'body-parser';
 import { join } from 'path';
 
 // 缓存 app 实例，避免每次冷启动都重新创建