Fix audio device not restored in settings: suppress callbacks during RefreshAudioDevices

RefreshAudioDevices was firing OnRXDevChange/OnTXDevChange when restoring
the combo selection, which called ApplyAudioDevice(-1,'') and wiped
FAudioOutDevName/FAudioInDevName before LoadValues could use them.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SettingsForm.pas

@@ -2051,6 +2051,7 @@ var
   OldTXSel: string;
 begin
   Names := TStringList.Create;
+  FLoading := True;
   try
     if AudioOut <> nil then
     begin
@@ -2098,6 +2099,7 @@ begin
       else FCmbTXDev.ItemIndex := 0;
     end;
   finally
+    FLoading := False;
     Names.Free;
   end;
 end;