- Add `splendor-gems` spritesheet (6 frames, 64×64) for gem icons.
- Introduce `gemFrame` helper to map gem colors to spritesheet indices.
- Update gem rendering in player bars, card badges, and cost pips to use sprites when available.
- Add `hasGems` flag to gracefully fallback to vector circles when art is missing.
- Register new asset in PreloadScene.