chore: migrate backend to monorepo apps and biome

apps/gateway/src/gateway.controller.spec.ts

@@ -0,0 +1,22 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { GatewayController } from './gateway.controller';
+import { GatewayService } from './gateway.service';
+
+describe('GatewayController', () => {
+  let gatewayController: GatewayController;
+
+  beforeEach(async () => {
+    const app: TestingModule = await Test.createTestingModule({
+      controllers: [GatewayController],
+      providers: [GatewayService],
+    }).compile();
+
+    gatewayController = app.get<GatewayController>(GatewayController);
+  });
+
+  describe('root', () => {
+    it('should return "Hello World!"', () => {
+      expect(gatewayController.getHello()).toBe('Hello World!');
+    });
+  });
+});