feat(FN-1704): add dashboard resume entry point for onboarding

- Add model-onboarding-state.ts module for persisting onboarding step state
- Create OnboardingResumeCard component with resume functionality
- Wire resume card into App.tsx (visible when onboarding is resumable and modal is closed)
- Add unit tests for state helpers and resume card
- Add integration tests for App.tsx resume card behavior
- Update documentation with resume banner behavior
- Fix missing contextVersionAtStart property declaration in useBadgeWebSocket.ts

packages/dashboard/app/hooks/useBadgeWebSocket.ts

@@ -74,6 +74,7 @@ class BadgeWebSocketStore {
   // from corrupting badge state after project switches.
   private previousProjectIdRef: string | null = null;
   private projectContextVersionRef = 0;
+  private contextVersionAtStart = 0;
 
   subscribe(listener: () => void): () => void {
     this.listeners.add(listener);