fix: replaying a QSO used the voice keyer's level and overdrove the rig

A panadapter shot settles it: answering an S5 station, the replayed recording
goes out several times wider and taller than the station being answered — in WAV
as well as MP3, so this is not the encoder.

One setting served two sources that have nothing in common. A voice-keyer
message is a microphone at speaking distance and legitimately wants 195%; a QSO
recording is a receiver's line output, which is far hotter. The same 195% put it
into the transmitter flat out, ALC pinned, noise and voice alike.

The QSO playback now has its own level, defaulting to 100%. The voice keyer
keeps the setting it had, so nobody's F-key messages change.

frontend/wailsjs/go/models.ts

@@ -1608,6 +1608,7 @@ export namespace main {
 	    from_gain: number;
 	    mic_gain: number;
 	    tx_gain: number;
+	    qso_play_gain: number;
 	
 	    static createFrom(source: any = {}) {
 	        return new AudioSettings(source);
@@ -1628,6 +1629,7 @@ export namespace main {
 	        this.from_gain = source["from_gain"];
 	        this.mic_gain = source["mic_gain"];
 	        this.tx_gain = source["tx_gain"];
+	        this.qso_play_gain = source["qso_play_gain"];
 	    }
 	}
 	export class AutostartLaunchResult {