Added

• Spectrum analyser — A live frequency display now sits behind the phase and filter curves, so you can see where your signal's energy lies across the band while you line things up. It follows whichever view you're in, Left/Right or Mid/Side.
• Custom channel colours — Pick your own colour for each channel: click the colour chip next to the Left/Right (or Mid/Side) label to recolour that channel's phase curve, filter, spectrum and accent bar. Your colours are saved with the session.

Initial release.