Fixed fatal error in ShippingController. Issue: - ShippingController extended BaseController (does not exist) - Caused PHP fatal error: Class not found Fix: - Changed to extend WP_REST_Controller (WordPress standard) - Matches pattern used by PaymentsController and StoreController - Added proper PHPDoc header Result: ✅ API endpoint now works ✅ No more 500 errors ✅ Shipping zones load correctly