Try HTTPS upgrade for HTTP streams, show error on failure

Browsers block HTTP (mixed content) audio from HTTPS pages. On playStation,
if the URL is http:// and page is https://, try the https:// version first.
If the stream fails to load, show a clear error in the track display instead
of silently doing nothing.

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

static/js/app.js

@@ -70,7 +70,25 @@ function playStation(url, name, stationId) {
   currentStation = { url, name, id: stationId || null };
   isPlaying = true;
 
-  audio.src = url;
+  // If page is HTTPS and stream is HTTP, try upgrading to HTTPS first.
+  // Browsers block mixed content (HTTP media on HTTPS pages).
+  const playUrl = (location.protocol === 'https:' && url.startsWith('http://'))
+    ? url.replace('http://', 'https://')
+    : url;
+
+  audio.onerror = () => {
+    const wasUpgraded = playUrl !== url;
+    if (wasUpgraded) {
+      $('now-playing-track').textContent = 'Stream nicht erreichbar (HTTP-only, kein HTTPS-Fallback)';
+    } else {
+      $('now-playing-track').textContent = 'Stream konnte nicht geladen werden';
+    }
+    isPlaying = false;
+    $('play-stop-btn').textContent = '▶ Play';
+    $('play-stop-btn').classList.remove('playing');
+  };
+
+  audio.src = playUrl;
   const volSlider = document.getElementById('volume');
   if (volSlider) audio.volume = volSlider.value / 255;
   audio.play().catch(() => {
@@ -113,6 +131,7 @@ function stopPlayback(clearStation = true) {
   audio.src = '';
   audio.ontimeupdate = null;
   audio.onended = null;
+  audio.onerror = null;
   isPlaying = false;
   podcastMode = false;
   if ('mediaSession' in navigator) navigator.mediaSession.playbackState = 'none';