- completely rewrite tetris game with improved architecture and design

- add modern responsive layout with flexbox and CSS variables
- implement hold piece functionality and next piece preview
- add game states (start, playing, paused, game over) with UI panels
- improve scoring system with levels and high score persistence
- add ghost piece visualization for better placement
- implement touch controls with dedicated button layout
- add settings menu with volume control and mute option
- improve visual design with gradients, shadows and semi-transparent elements
- implement proper game speed acceleration based on level

Author: TobiasMue91