Implemented variable playback speed functionality:
- Added playbackRate state and ref to useMultiTrackPlayer (0.25x - 2x range)
- Applied playback rate to AudioBufferSourceNode.playbackRate
- Updated timing calculations to account for playback rate
- Real-time playback speed adjustment for active playback
- Dropdown UI control in PlaybackControls with preset speeds
- Integrated changePlaybackRate function through AudioEditor
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Co-Authored-By: Claude <noreply@anthropic.com>
Sebastian Krüger
9007522e18