Normalize game architecture

lib/ui/screens/game_page.dart

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/app_bar.dart

lib/ui/widgets/bottom_nav_bar.dart

lib/ui/widgets/game/cell.dart

lib/ui/widgets/game/game_board.dart

lib/ui/widgets/game/indicator_top.dart

lib/ui/widgets/game/message_game_end.dart

lib/ui/widgets/game/mode_button_toggle.dart

lib/ui/widgets/game/mode_indicator_report.dart

lib/ui/widgets/game/mode_indicator_walk.dart