- Add Group and GroupMember models with CRUD service methods
- Implement social group endpoints: create, list, get, join, leave
- Add WishlistItem model with get/add/remove service methods
- Add CartItem model with get/add/remove/checkout service methods
- Create handlers for marketplace wishlist and cart operations
- Register playlist export (JSON/CSV) and duplicate routes
- Enable PLAYLIST_SHARE and NOTIFICATIONS feature flags
Co-authored-by: Cursor <cursoragent@cursor.com>