init：创建后端项目框架，确保环境的基本运行

src/main.ts

@@ -0,0 +1,10 @@
+import { NestFactory } from '@nestjs/core';
+import { AppModule } from './app.module';
+
+async function bootstrap() {
+  const app = await NestFactory.create(AppModule);
+  await app.listen(3000);
+  console.log('Pixel Game Server is running on http://localhost:3000');
+}
+
+bootstrap();