Watch Together: Embed-Fehlerbehandlung, klickbare Queue, Video-Titel

- YouTube onError Handler: Erkennt Error 101/150 (Embedding deaktiviert),
  zeigt Fehlermeldung + "Auf YouTube oeffnen" Link, auto-skip nach 3s
- Queue-Items klickbar fuer Host (play_video mit Index)
- Video-Titel werden via noembed.com oEmbed API geholt
- Server-Endpoint: GET /api/watch-together/video-info?url=...
- "Hinzufuegen" Button zeigt Ladezustand waehrend Titel-Fetch

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

web/src/plugins/watch-together/watch-together.css

@@ -651,6 +651,57 @@
   flex-shrink: 0;
 }
 
+/* ── Player Error Overlay ── */
+.wt-player-error {
+    position: absolute;
+    inset: 0;
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    gap: 12px;
+    background: rgba(0, 0, 0, 0.85);
+    color: #fff;
+    z-index: 2;
+    text-align: center;
+    padding: 20px;
+}
+.wt-error-icon {
+    font-size: 48px;
+}
+.wt-player-error p {
+    font-size: 15px;
+    color: var(--text-muted);
+    margin: 0;
+}
+.wt-yt-link {
+    display: inline-block;
+    padding: 8px 20px;
+    background: #ff0000;
+    color: #fff;
+    border-radius: var(--radius);
+    text-decoration: none;
+    font-weight: 600;
+    font-size: 14px;
+    transition: background var(--transition);
+}
+.wt-yt-link:hover {
+    background: #cc0000;
+}
+.wt-skip-info {
+    font-size: 12px !important;
+    color: var(--text-faint) !important;
+    font-style: italic;
+}
+
+/* ── Clickable Queue Items ── */
+.wt-queue-item.clickable {
+    cursor: pointer;
+}
+.wt-queue-item.clickable:hover {
+    background: rgba(230, 126, 34, 0.12);
+}
+
 /* ══════════════════════════════════════
    RESPONSIVE
    ══════════════════════════════════════ */