Add MasterBus component + enhance BusStrip with routing selector

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.

daemon/oplabs-mixer-daemon.service.in

@@ -0,0 +1,25 @@
+[Unit]
+Description=OPLabs Mixer Daemon
+Documentation=https://git.ourpad.casa/oplabs/oplabs-mixer-app
+After=network.target sound.target
+Wants=jack.service
+
+[Service]
+Type=simple
+User=oplabs
+ExecStart=/usr/bin/oplabs-mixer-daemon \
+    --socket-path /tmp/oplabs-mixer.sock \
+    --sample-rate 48000 \
+    --buffer-size 512 \
+    --input-channels 8 \
+    --output-channels 8
+Restart=on-failure
+RestartSec=5
+LimitNOFILE=8192
+Nice=-10
+
+# JACK-specific: wait for JACK to be ready
+ExecStartPre=/bin/sh -c 'while ! jack_wait -c 2>/dev/null; do sleep 1; done'
+
+[Install]
+WantedBy=multi-user.target