Brand catalog now follows the same navigation as the regular catalog:
1. Brands -> 2. Models -> 3. Years -> 4. Engines -> 5. Categories -> 6. Parts
Backend:
- Add /mye-parts endpoint for MYE-specific parts with category filter
- Uses existing /models, /years, /engines, /categories endpoints
Frontend:
- Complete rewrite of brand-catalog.js with breadcrumb navigation
- State machine: brands -> models -> years -> engines -> categories -> parts
- Search and pagination preserved at parts level
- Breadcrumb allows jumping back to any previous step