- Add promo preference fields to User model (promo_preferred_maker,
promo_preferred_model, promo_email_enabled)
- Create API endpoints for getting/updating promo preferences
- Create PromoPreference component with maker/model selection
- Show login prompt for non-logged-in users when interacting
- Add promo notification service to send emails when matching vehicles
are added to promotion
- Add multi-language translations (en, mn, ru, ko)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>