Integrate audio feedback across the game by adding new SFX assets and loading them in `BootScene`. Key changes include:
- Added 12 new sound effect files (attacks, abilities, UI) and a main menu music track.
- Implemented SFX playback in `BattleScene` for actions like attacks, counters, mortar/strike/siege/pierce fires, buffs (rally), shields (protect), damage, destructions, and legendary card plays.
- Stopped main menu music during battles to avoid audio overlap and resumed it upon returning to `MainMenuScene`.
- Added hover and select sounds for UI buttons in `MainMenuScene`.
- Fixed deck composition in `DeckManager` by removing one 'imp_trooper_1' from the starter deck.
