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.

frontend/app/Navigation.tsx

@@ -38,6 +38,7 @@ export default async function Navigation() {
       {(session?.user as any)?.role === 'admin' && (
         <>
           <Link href="/admin/products" style={linkStyle}>⚙️ Admin</Link>
+          <Link href="/admin/products/pending" style={linkStyle}>⏳ Förslag</Link>
           <Link href="/profil?tab=anvandare" style={linkStyle}>👥 Användare</Link>
         </>
       )}