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

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

backend/src/AppModule.ts

@@ -0,0 +1,15 @@
+import { Module } from '@nestjs/common';
+import { ConfigModule } from '@nestjs/config';
+import appConfig from './config';
+import { HealthCheckModule } from './modules/healthCheck/HealthCheckModule';
+
+@Module({
+    imports: [
+        ConfigModule.forRoot({
+            isGlobal: true,
+            load: [appConfig]
+        }),
+        HealthCheckModule
+    ]
+})
+export class AppModule {}