Implemented Phase 11.1 export format support:
- Added MP3 export using lamejs library
- Added FLAC export using fflate DEFLATE compression
- Updated ExportDialog with format selector and format-specific options
- MP3: bitrate selector (128/192/256/320 kbps)
- FLAC: compression quality slider (0-9)
- WAV: bit depth selector (16/24/32-bit)
- Updated AudioEditor to route export based on selected format
- Created TypeScript declarations for lamejs
- Fixed AudioStatistics to use audioBuffer instead of buffer property
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Co-Authored-By: Claude <noreply@anthropic.com>