refactor: standardize new game progress ui

- introduce shared progress indicator component for wizard steps
- align layouts and button sizing across new game panels
- update feature exports to surface the new component

Refs #30

src/lib/features/new-game/index.ts

@@ -6,4 +6,5 @@ export { GameTypeStep } from './steps/GameTypeStep';
 export { RaceToStep } from './steps/RaceToStep';
 export { BreakRuleStep } from './steps/BreakRuleStep';
 export { BreakOrderStep } from './steps/BreakOrderStep';
+export { ProgressIndicator } from './ProgressIndicator';