feat(innovation): audio-reactive LED visualizer — Phase 1 complete

Innovation Day — Audio Reactive LED Strip

Implements Phase 1: FFT Core with logarithmic band splitting.

Changes

• AudioProcessor.buildBinToBandMap() — constant-Q perceptual bands (20Hz–Nyquist)
• Replace linear averaging with proper bin→band accumulation
• TypeScript strict mode fixes

Acceptance

• audio.getBands(60) returns live 0–1 normalized array
• Smoothing applied per-band (configurable via setSmoothing)
• tsc --noEmit clean, npm run build succeeds

Next

Phase 2 — Canvas 2D renderer enhancements + ControlPanel UI

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Innovation Day sprint