fix(favorites): adjust favorite button visibility and functionality

- removed favorite button from Discover cards

- added call button for taxis in Favorites view

- added favorite button in Shuttle details

- added Shuttles category in Favorites view

frontend/src/components/FavoriteButton.vue

@@ -17,7 +17,7 @@ import { useFavoritesStore } from '@/stores/favorites'
 import { useAuthStore } from '@/stores/auth'
 
 const props = defineProps<{
-  itemType: 'coupon' | 'business' | 'taxi' | 'route' | 'stop'
+  itemType: 'coupon' | 'business' | 'taxi' | 'route' | 'stop' | 'shuttle'
   itemId: string
   itemName?: string
   itemImage?: string