- Added new sound effect and music MP3 files to the project.
- Updated **BootScene** to preload all music tracks and sound effects.
- Implemented music playback:
* MenuScene now plays looping title music and stops it on shutdown.
* GameScene now stops any playing music on shutdown and starts level‑specific background music with fallback to the last track.
- Added SFX triggers for player shooting, alien shooting, missile launch, impacts, alien death, and player death.
- Cleaned up formatting and minor code style issues in GameScene (group/array declarations, tweens, UI text creation, level setup loops, etc.).
- Ensured proper cleanup of music objects when scenes change.
