feat(feature): add delete item option for Jellyfin admin accounts

[Arnab11]

• Add deleteItem method to AdminRepository and JellyfinAdminRepository using Jellyfin SDK LibraryApi.
• Add AdminAction.Delete to AdminAction interface and add a styled Delete menu item under the triple-dot options menu in ActionButtonsRow and EpisodeDetailOverlay (visible only when isAdmin is true).
• Inject AdminRepository into ItemDetailViewModel and add deleteItem method with success/failure callbacks and change notification via AdminChangeBroadcaster.
• Add DeleteConfirmationDialog to ItemDetailScreen warning admins before deleting media files from the server, popping the navigation stack on main item deletion.
• Add string resources for delete dialog title, message, success, and error notifications.