Normalize game architecture

lib/ui/screens/page_about.dart

lib/ui/screens/page_game.dart

lib/ui/screens/page_settings.dart

lib/ui/settings/settings_form.dart

lib/ui/settings/theme_card.dart

lib/ui/skeleton.dart

lib/ui/widgets/actions/button_delete_saved_game.dart

lib/ui/widgets/actions/button_game_quit.dart

lib/ui/widgets/actions/button_game_start_new.dart

lib/ui/widgets/actions/button_resume_saved_game.dart

lib/ui/widgets/game/game.dart

lib/ui/widgets/game/game_board.dart

lib/ui/widgets/game/game_shuffling.dart

lib/ui/widgets/game/game_tile.dart

lib/ui/widgets/game/game_tileset.dart

lib/ui/widgets/game/game_tip.dart

lib/ui/widgets/global_app_bar.dart

lib/ui/widgets/indicators/indicator_score.dart

lib/utils/color_extensions.dart

lib/utils/game_utils.dart