feat(api): cn-app skeleton, toolchain, env loading convention

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

services/api/src/main-cn.ts

@@ -0,0 +1,26 @@
+// services/api/src/main-cn.ts
+// cn-app 部署入口（P1a 仅此一个 API 入口）。构建产物 dist/main-cn.js 由根 dev:api /
+// 生产启动命令运行；env 一律来自进程环境（根 dotenv-cli 注入），此处不读文件。
+import 'reflect-metadata';
+import { type INestApplication } from '@nestjs/common';
+import { NestFactory } from '@nestjs/core';
+import { Logger } from 'nestjs-pino';
+import { AppCnModule } from './app-cn.module';
+
+async function bootstrap(): Promise<void> {
+  const app = await NestFactory.create<INestApplication>(AppCnModule, {
+    bufferLogs: true,
+  });
+  app.useLogger(app.get(Logger));
+  app.setGlobalPrefix('v1');
+  const corsOrigins = (process.env.CORS_ORIGINS ?? 'http://localhost:5173')
+    .split(',')
+    .map((origin) => origin.trim())
+    .filter((origin) => origin !== '');
+  app.enableCors({ origin: corsOrigins });
+  const port = Number.parseInt(process.env.PORT ?? '', 10) || 8080;
+  await app.listen(port);
+  app.get(Logger).log(`api-cn listening on port ${port}`);
+}
+
+void bootstrap();