Clarify and decompose Race Mode UX

[burkben]

Summary

• add an explicit Solo / Race night setup flow with portal-readiness start gating and Speed-tab recovery
• make current racer, up next, car assignments, start, and advance actions unambiguous with identified catalog names/photos
• decompose the Race route into feature-local setup, lineup, countdown, progress, results, leaderboard, presentation, and lifecycle modules
• add accessible labels/states plus guarded countdown, lap, best-time, and finish announcements
• correct the durable leaderboard copy while preserving race-engine, persistence, transport, reduced-motion, haptics, and per-lineup assignment behavior

Validation

• npm test
• npm run typecheck
• npx expo export --platform ios --output-dir /tmp/hotwheelsid-race-ios