Stop the voice-queue poller when the payload is not what it expects

pollVoiceQueue began with 'if (!s || !s.items) return;'. On an unexpected
payload that returned before the code that clears the interval, so a page
left open polled /api/voices/queue every 2s forever. The web log shows 626
such polls - about 21 minutes of continuous requests from a browser through
the Caddy proxy, with CLOSE_WAIT sockets accumulating alongside.

An unexpected response now stops the poll rather than skipping the check.
Verified in a real browser against a deliberately malformed payload: one
request, then stopped, where it previously never stopped.

umbraaudio/web/templates/speakers.html

@@ -358,6 +358,13 @@ function applyQueueState(name, status, error) {
 
 var _vqPoll = null;
 
+function stopVoiceQueuePolling() {
+    if (_vqPoll) {
+        clearInterval(_vqPoll);
+        _vqPoll = null;
+    }
+}
+
 function startVoiceQueuePolling() {
     if (_vqPoll) return;
     _vqPoll = setInterval(pollVoiceQueue, 2000);
@@ -366,7 +373,13 @@ function startVoiceQueuePolling() {
 
 function pollVoiceQueue() {
     fetch('/api/voices/queue').then(function(r) { return r.json(); }).then(function(s) {
-        if (!s || !s.items) return;
+        // An unexpected payload must STOP the poll, not skip the check. The
+        // bare return that used to be here left the interval running forever,
+        // so a page left open hit /api/voices/queue every 2s indefinitely.
+        if (!s || !Array.isArray(s.items)) {
+            stopVoiceQueuePolling();
+            return;
+        }
         var anyPending = false;
         s.items.forEach(function(item) {
             applyQueueState(item.speaker_name, item.status, item.error || '');
@@ -374,9 +387,8 @@ function pollVoiceQueue() {
         });
         // Stop polling once nothing is outstanding, and refresh the list so the
         // new audio file / voice badge appears without a manual reload.
-        if (!anyPending && _vqPoll) {
-            clearInterval(_vqPoll);
-            _vqPoll = null;
+        if (!anyPending) {
+            stopVoiceQueuePolling();
             refreshSpeakerRow(null);
         }
     }).catch(function() {});