- Add PNG artwork assets for Imperial and Raider faction cards (commanders and units).
- Update `BootScene` to dynamically load card images based on `artKey` entries in `cards.json`.
- Refactor `CardObject` to render the loaded image over a faction-colored backing, falling back gracefully if the texture is missing.
- Replace the previous solid background rectangle with a transparent red overlay (`.bg`) for the attack flash animation, ensuring art remains visible during impacts.
