add NestJS skeleton and GET /api/health-check.

Thin API bootstrap with config module and nullcart-style health route for Docker checks.

backend/src/main.ts

@@ -0,0 +1,30 @@
+import { ValidationPipe } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { NestFactory } from '@nestjs/core';
+import { AppModule } from './AppModule';
+import { AppConfig } from './types/AppConfig';
+
+async function bootstrap() {
+    const app = await NestFactory.create(AppModule);
+
+    const configService = app.get(ConfigService);
+    const { port, corsOrigins } = configService.get('app') as AppConfig;
+
+    app.setGlobalPrefix('api');
+
+    app.useGlobalPipes(
+        new ValidationPipe({
+            transform: true,
+            transformOptions: { enableImplicitConversion: true }
+        })
+    );
+
+    app.enableCors({
+        origin: corsOrigins,
+        credentials: true
+    });
+
+    await app.listen(port);
+}
+
+void bootstrap();