feat: implement real-time database synchronization with SSE and update backend modules

backend/src/app.module.ts

@@ -16,6 +16,7 @@ import { UsersModule } from './users/users.module';
 import { UserProductsModule } from './user-products/user-products.module';
 import { CategoriesModule } from './categories/categories.module';
 import { AiModule } from './ai/ai.module';
+import { RealtimeModule } from './realtime/realtime.module';
 import { JwtAuthGuard } from './auth/jwt-auth.guard';
 import { RolesGuard } from './auth/roles.guard';
 
@@ -44,6 +45,7 @@ import { RolesGuard } from './auth/roles.guard';
     UserProductsModule,
     CategoriesModule,
     AiModule,
+    RealtimeModule,
   ],
   providers: [
     {