perf: reduce queue and autoplay memory footprint

src/view/maintoolbar.hpp

@@ -55,6 +55,13 @@ private slots:
     void onAlbumArtReady(QNetworkReply *reply);
 
 private:
+    struct RecentTrackSeed {
+        qint64 trackId = 0;
+        qint64 artistId = 0;
+        qint64 genreId = 0;
+        qint64 labelId = 0;
+    };
+
     QobuzBackend *m_backend = nullptr;
     PlayQueue    *m_queue   = nullptr;
 
@@ -76,7 +83,7 @@ private:
     QNetworkAccessManager *m_nam = nullptr;
     QString     m_currentArtUrl;
     QJsonObject m_currentTrack;
-    QVector<QJsonObject> m_recentTracks;
+    QVector<RecentTrackSeed> m_recentTracks;
     bool        m_playing = false;
     bool        m_seeking = false;
     bool        m_fetchingAutoplay = false;