feat(categories): implement category management with hierarchical structure and update product association

backend/src/app.module.ts

@@ -13,6 +13,7 @@ import { ReceiptAliasModule } from './receipt-alias/receipt-alias.module';
 import { AuthModule } from './auth/auth.module';
 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';
 
 
@@ -31,6 +32,7 @@ import { JwtAuthGuard } from './auth/jwt-auth.guard';
     AuthModule,
     UsersModule,
     UserProductsModule,
+    CategoriesModule,
   ],
   providers: [
     {