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

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

services/api/src/health.controller.ts

@@ -0,0 +1,11 @@
+// services/api/src/health.controller.ts
+// GET /v1/health —— 存活探针（P1a 仅此一个端点，后续任务逐步扩展）。
+import { Controller, Get } from '@nestjs/common';
+
+@Controller('health')
+export class HealthController {
+  @Get()
+  check(): { status: 'ok' } {
+    return { status: 'ok' };
+  }
+}