Fixes deep-link close to preserve browser history state and adds comprehensive integration tests for the navigation history feature, covering App component and useDeepLink hook behavior.
Fusion-Task-Id: FN-3344
- Extract modal manager, app settings, deep-link handling, favorites, and auth onboarding into dedicated hooks
- Rewire App.tsx to consume the new hooks and reduce component-level state/effect complexity
- Preserve favorite-toggle error toast behavior in the updated favorites wiring
- Add hook-level test coverage for modal manager, app settings, deep links, favorites, and auth onboarding flows
