feat: implement responsive design enhancements

- Add touch-optimized tap targets (44x44px minimum for iOS)
- Enhance mobile responsiveness across all components
- Improve button sizing and spacing for touch interactions
- Add responsive text sizing and layout adjustments
- Implement mobile-first modal behavior (bottom sheet on mobile)
- Enhance form controls with better touch targets
- Add active states for better touch feedback
- Improve grid layouts for various screen sizes
- Add smooth scrolling and better focus states
- Optimize FilterPanel for mobile with grid layouts
- Enhance all interactive elements with tap-target classes

Requirements: 7.1, 7.2

.kiro/specs/ultimate-lists-app/tasks.md

@@ -184,7 +184,7 @@
   - Test "Add to Home Screen" functionality in Safari
   - _Requirements: 4.1, 4.2_
 
-- [ ] 14. Implement responsive design enhancements
+- [x] 14. Implement responsive design enhancements
   - Ensure all components are mobile-responsive
   - Add touch-optimized controls (larger tap targets)
   - Test on various screen sizes