feat(cat): MY_RIG follows the radio that is connected

With one rig, MY_RIG belonged in Operating conditions and nowhere else.
With several, that becomes the wrong place: operating conditions describe
a PLAN — 'on 20 m I use the beam and the 7300' — while the question a
logged QSO asks is which radio was keying.

So each saved radio carries its own MY_RIG, consulted BEFORE the per-band
station. When the two disagree — a second rig borrowed for one evening on
20 m — the one that is transmitting is the true answer.

Left empty it changes nothing at all: the old chain (band default, then
the profile's rig) answers exactly as it did, which is what every
single-radio station will keep doing without touching a setting.

frontend/wailsjs/go/models.ts

@@ -3573,6 +3573,7 @@ export namespace main {
 	    id: string;
 	    name: string;
 	    settings: CATSettings;
+	    my_rig: string;
 	
 	    static createFrom(source: any = {}) {
 	        return new RadioConfig(source);
@@ -3583,6 +3584,7 @@ export namespace main {
 	        this.id = source["id"];
 	        this.name = source["name"];
 	        this.settings = this.convertValues(source["settings"], CATSettings);
+	        this.my_rig = source["my_rig"];
 	    }
 	
 		convertValues(a: any, classs: any, asMap: boolean = false): any {