Fix loopback device status showing 'Unavailable' after change

The POST /visualizer/device response has 'success' but no 'available'
field, causing updateAudioDeviceStatus to always fall to 'Unavailable'.

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

media_server/static/js/player.js

@@ -494,7 +494,7 @@ async function onAudioDeviceChanged() {
 
         if (resp.ok) {
             const result = await resp.json();
-            updateAudioDeviceStatus(result);
+            updateAudioDeviceStatus({ available: result.success, ...result });
             await checkVisualizerAvailability();
             if (visualizerEnabled) applyVisualizerMode();
             showToast(t('settings.audio.device_changed'), 'success');