fix(audio): the Listen button works with the network stream as the source

Its enable condition predated the network audio: with From-radio empty — the
normal network setup — the button was greyed out, and an operator who had
stopped listening had no way to start again from this panel. The stale 'later'
hints on both buttons said the network paths did not exist; they do.

frontend/src/components/SettingsModal.tsx

@@ -6988,7 +6988,8 @@ function SettingsModalImpl({ onClose, onSaved, initialSection, onMainPaneChanged
               size="sm"
               className="h-8"
               onClick={toggleMonitor}
-              disabled={!monitorOn && (!audioCfg.from_radio || fromRadioIsNetwork)}
+              disabled={!monitorOn && (!audioCfg.from_radio || fromRadioIsNetwork)
+                && !(catCfg.backend === 'icom-net' && (catCfg as any).icom_net_audio)}
               title={fromRadioIsNetwork ? t('aud.monitorNoTci') : t('aud.monitorTitle')}
             >
               {monitorOn ? t('aud.stopListening') : t('aud.listenRadio')}