feat: add smooth animations for BST insert/delete operations

- Add animated insertion with step-by-step path traversal (amber/yellow highlighting)
- Add animated deletion with red highlight and pulsing glow effect
- Show 'Inserting...' and 'Deleting...' button states during operations
- Implement proper animation cleanup with 600ms insertion steps and 800ms deletion delay
- Fix root node deletion to properly update isRoot flag on new root
- Fix animation states getting stuck on root deletion
- Add visual states: Green (root/new), White (regular), Blue (search), Amber (insert), Red (delete)
- Update legend to include Insert Path and Deleting states (6 total states)
- Disable buttons during animations to prevent concurrent operations
- Add TypeScript type annotation for insertion traversal logic
- Ensure smooth 60fps animations with CSS transitions and pulsing effects

All operations now have consistent, educational, step-by-step visual feedback matching the search animation quality.

Author: mnaimfaizy