fix: art scaling on shrink + skip unavailable tracks in queue

- Now-playing art: use setFixedHeight (not setFixedSize) so the dock
  width constraint is removed and can shrink freely; use event->size()
  in resizeEvent to get the correct new width without layout lag
- PlayQueue: filter non-streamable tracks out of setContext and
  reorderContext so unavailable tracks are never in the queue and
  pressing Next always lands on a playable track

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

src/playqueue.hpp

@@ -25,14 +25,27 @@ public:
     {
         m_queue.clear();
         m_playNext.clear();
-        for (const auto &v : tracks)
-            m_queue.append(v.toObject());
-        if (m_shuffle) {
-            shuffleQueue(startIndex);
-            // shuffleQueue moves the start track to index 0 and sets m_index = 0
-        } else {
-            m_index = qBound(0, startIndex, m_queue.size() - 1);
+
+        // Only queue streamable tracks; find the filtered index for startIndex
+        int filteredStart = 0;
+        int filteredIdx   = 0;
+        bool found        = false;
+        for (int orig = 0; orig < tracks.size(); ++orig) {
+            const QJsonObject t = tracks[orig].toObject();
+            if (!t["streamable"].toBool(true))
+                continue;
+            if (!found && orig >= startIndex) {
+                filteredStart = filteredIdx;
+                found = true;
+            }
+            m_queue.append(t);
+            ++filteredIdx;
         }
+        m_index = qBound(0, filteredStart, qMax(0, m_queue.size() - 1));
+
+        if (m_shuffle)
+            shuffleQueue(m_index);
+
         emit queueChanged();
     }
 
@@ -41,8 +54,11 @@ public:
     void reorderContext(const QJsonArray &tracks, qint64 currentId)
     {
         m_queue.clear();
-        for (const auto &v : tracks)
-            m_queue.append(v.toObject());
+        for (const auto &v : tracks) {
+            const QJsonObject t = v.toObject();
+            if (t["streamable"].toBool(true))
+                m_queue.append(t);
+        }
 
         m_index = 0;
         for (int i = 0; i < m_queue.size(); ++i) {