feat: initial qobuz-qt source

Lightweight Qt6 desktop client for Qobuz with a Rust audio backend
(Symphonia/CPAL via staticlib FFI). Mirrors the spotify-qt layout:
toolbar with playback controls, library/context docks on the left,
tabbed search side panel on the right, queue panel, now-playing dock.

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

src/view/maincontent.hpp

@@ -2,21 +2,20 @@
 
 #include "../list/tracks.hpp"
 #include "../backend/qobuzbackend.hpp"
+#include "../playqueue.hpp"
 
 #include <QWidget>
 #include <QLabel>
 #include <QStackedWidget>
-#include <QJsonArray>
 #include <QJsonObject>
+#include <QJsonArray>
 
-/// Central content widget — mirrors MainContent from spotify-qt.
-/// Displays either a track list, an album cover + tracks, or a search result.
 class MainContent : public QWidget
 {
     Q_OBJECT
 
 public:
-    explicit MainContent(QobuzBackend *backend, QWidget *parent = nullptr);
+    explicit MainContent(QobuzBackend *backend, PlayQueue *queue, QWidget *parent = nullptr);
 
     List::Tracks *tracksList() const { return m_tracks; }
 
@@ -27,8 +26,8 @@ public:
     void showSearchTracks(const QJsonArray &tracks);
 
 private:
-    QobuzBackend    *m_backend = nullptr;
-    QStackedWidget  *m_stack   = nullptr;
-    QLabel          *m_welcome = nullptr;
-    List::Tracks    *m_tracks  = nullptr;
+    QobuzBackend   *m_backend = nullptr;
+    QStackedWidget *m_stack   = nullptr;
+    QLabel         *m_welcome = nullptr;
+    List::Tracks   *m_tracks  = nullptr;
 };