MAJOR UPPDATE: "First Ai"

feat: add AI categorization for products and enhance user management

- Integrated AI service for category suggestions in receipt import and product management.
- Added premium subscription feature for users with corresponding API endpoints.
- Implemented admin interface for managing pending product suggestions.
- Enhanced user management to include premium status and corresponding UI updates.
- Updated database schema to support new fields for premium status and product status.

backend/src/ai/ai.module.ts

@@ -0,0 +1,8 @@
+import { Module } from '@nestjs/common';
+import { AiService } from './ai.service';
+
+@Module({
+  providers: [AiService],
+  exports: [AiService],
+})
+export class AiModule {}