refactor: migrate backend framework from Express to NestJS

src/health.controller.ts

@@ -0,0 +1,9 @@
+import { Controller, Get } from '@nestjs/common';
+
+@Controller('health')
+export class HealthController {
+  @Get()
+  check() {
+    return { status: 'ok', message: '服务器运行正常' };
+  }
+}