refactor: 统一代码缩进与引号风格，新增CORS配置

1.  修正所有文件的缩进为4空格，将单引号统一改为双引号
2.  新增CORS_ORIGIN环境变量配置并从env读取CORS允许源
3.  新增prettier配置文件统一代码格式
4.  为main.ts添加启动日志输出

src/main.ts

@@ -1,12 +1,13 @@
-import 'dotenv/config';
-import { NestFactory } from '@nestjs/core';
-import { AppModule } from './app.module';
-import { bootstrapApp } from './bootstrap';
+import "dotenv/config";
+import { NestFactory } from "@nestjs/core";
+import { AppModule } from "./app.module";
+import { bootstrapApp } from "./bootstrap";
 
 async function bootstrap() {
-  const app = await NestFactory.create(AppModule);
-  bootstrapApp(app);
-  await app.listen(process.env.PORT ?? 3000);
+    const app = await NestFactory.create(AppModule);
+    bootstrapApp(app);
+    await app.listen(process.env.PORT ?? 3000);
+    console.log(`Application is running on: ${await app.getUrl()}`);
 }
 
 void bootstrap();