chore: migrate backend to monorepo apps and biome

apps/gateway/src/gateway.module.ts

@@ -0,0 +1,10 @@
+import { Module } from '@nestjs/common';
+import { GatewayController } from './gateway.controller';
+import { GatewayService } from './gateway.service';
+
+@Module({
+  imports: [],
+  controllers: [GatewayController],
+  providers: [GatewayService],
+})
+export class GatewayModule {}