feat(api): app NestJS con configuración validada y health check

Nest 12 (ESM, vitest, oxlint). El .env se valida con zod al arrancar;
prefijo global /api, CORS configurable y GET /api/health.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

apps/api/src/main.ts

@@ -0,0 +1,19 @@
+import { NestFactory } from '@nestjs/core';
+import type { LogLevel } from '@nestjs/common';
+import { AppModule } from './app.module.js';
+import { AppConfigService } from './config/app-config.service.js';
+
+const LOG_LEVELS: LogLevel[] = ['error', 'warn', 'log', 'debug', 'verbose'];
+
+async function bootstrap() {
+  const app = await NestFactory.create(AppModule);
+  const config = app.get(AppConfigService);
+
+  app.setGlobalPrefix('api');
+  app.useLogger(LOG_LEVELS.slice(0, LOG_LEVELS.indexOf(config.get('LOG_LEVEL')) + 1));
+  app.enableCors({ origin: config.get('CORS_ORIGINS') });
+  app.enableShutdownHooks();
+
+  await app.listen(config.get('PORT'));
+}
+await bootstrap();