feat(auth): implement role-based access control and user management features

backend/src/app.module.ts

@@ -15,6 +15,7 @@ import { UsersModule } from './users/users.module';
 import { UserProductsModule } from './user-products/user-products.module';
 import { CategoriesModule } from './categories/categories.module';
 import { JwtAuthGuard } from './auth/jwt-auth.guard';
+import { RolesGuard } from './auth/roles.guard';
 
 
 @Module({
@@ -39,6 +40,10 @@ import { JwtAuthGuard } from './auth/jwt-auth.guard';
       provide: APP_GUARD,
       useClass: JwtAuthGuard,
     },
+    {
+      provide: APP_GUARD,
+      useClass: RolesGuard,
+    },
   ],
 })
 export class AppModule {}