Home Assistant Dashboard picker registry fix.
- Mutates the existing window.customCards array in place instead of replacing it, matching Home Assistant's picker implementation which imports and keeps the original array reference.
- Bumped the package/card version to 5.1.5 and rebuilt dist.
Verification:
- npm run build
- npm run lint (warnings only)
- npm test: 60 passed
- node --check src/homeii-music-flow.js
- node --check dist/homeii-music-flow.js