Merges FN-3341 mobile keyboard handling improvements into the dashboard, wiring `useMobileKeyboard` into both TodoModal and PlanningModeModal with keyboard-aware CSS overrides for mobile, plus regression tests for both components. FN-3337's chat `isGenerating` state recovery is also included.
Fusion-Task-Id: FN-3341
- Add TodoModal component and styling, and mount it through AppModals
- Remove dedicated Todos view routing and drive todos access through modal state/actions
- Update Header and MobileNavBar interactions plus modal manager/view-state hooks for modal flow
- Expand dashboard tests to cover modal rendering, open/close behavior, and updated app/header expectations
Fusion-Task-Id: FN-3104
