- Fix volume sliders by tracking currentVolume separately from mute state
- Add song structure system with intro, verse, bridge, chorus, outro sections
- Implement automatic section transitions during playback based on duration
- Add 30-second loading bar with progress animation during beat generation
- Update instrument box colors (grey drums, red bass, green piano, baby blue brass)
- Add custom trumpet SVG icon for brass section
- Set duration slider max to 3 minutes
- Fix TypeScript type errors in audio engine classes
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
