Changed spectrogram to use transparency for low values instead of interpolating from background color: - Low signal values (0-64) fade from transparent to blue - Background color shows through transparent areas - Now matches FrequencyAnalyzer theme behavior - Both analyzers use bg-muted/30 wrapper for consistent theming 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>