shawn
d19e0ea7a8
MasterBus: stereo master fader, mute, level meters in PiPedal theme (purple accent per mixer-engine branch reference). BusStrip: added per-channel routing selector (ch1Route..ch8Route) for selecting output bus target (Main, Bus 2-8). MixerPage: integrated MasterBus with levels derived from bus master data. Local state for volume/mute until backend exposes master output.