fix: the audio level sliders did nothing until Settings were saved

Reported again after the monitor was wired up: 300% still sounded like 10%. The
monitor fix was right but could not show, because the sliders only changed the
settings panel's own state — the value reached the audio engine when the
operator clicked Save.

A level is set by ear, by dragging. It now applies on every move, to the monitor
and to the recorder mix alike; saving still persists it. Both halves were needed
and neither works alone.

frontend/wailsjs/go/main/App.js

@@ -70,6 +70,10 @@ export function AssignAwardRefToQSOs(arg1, arg2, arg3) {
   return window['go']['main']['App']['AssignAwardRefToQSOs'](arg1, arg2, arg3);
 }
 
+export function AudioApplyLevels(arg1, arg2) {
+  return window['go']['main']['App']['AudioApplyLevels'](arg1, arg2);
+}
+
 export function AudioMonitorActive() {
   return window['go']['main']['App']['AudioMonitorActive']();
 }