Simon Says: Improve implementation, UI, and add dark/light themes

### Project slug (e.g., snake, todo)

simon-says

### Summary

Rework the Simon Says game for smoother gameplay, better animations, and a refined UI. Add dark and light theme support with a toggle button. Enhance the color sequence highlighting and make transitions more visually appealing.

### Details / Acceptance criteria

Smooth and responsive color pad animations.

Proper sequence display with clear visual/audio cues.

Add dark and light mode toggle; theme persists between sessions.

UI improved with rounded buttons, glow effects, and score display.

Game logic optimized to prevent lag and handle restart gracefully.

### Scope

- [x] UI changes
- [x] Logic changes
- [x] Accessibility
- [x] Tests (manual)