Initial implementation of qobuz-qt

- Rust backend (qobuz-backend static lib): Qobuz API client (reqwest/tokio),
  Symphonia audio decoder, CPAL audio output, extern "C" FFI bridge
- Qt 6 frontend mirroring spotify-qt layout: toolbar with playback controls,
  left library dock, central track list, right search panel
- Auth: email/password login with MD5-signed requests; session token persisted
  via QSettings
- Playback: double-click a track → Rust fetches stream URL → Symphonia decodes
  → CPAL outputs to default audio device
- Dark Fusion palette matching spotify-qt feel

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

src/model/tracklistmodel.hpp

@@ -0,0 +1,57 @@
+#pragma once
+
+#include <QAbstractTableModel>
+#include <QJsonArray>
+#include <QJsonObject>
+#include <QVector>
+
+/// Flat data stored for each row in the track list.
+struct TrackItem {
+    qint64  id          = 0;
+    int     number      = 0;
+    QString title;
+    QString artist;
+    QString album;
+    QString albumId;
+    qint64  duration    = 0;   // seconds
+    bool    hiRes       = false;
+    bool    streamable  = false;
+    QJsonObject raw;           // full JSON for context menus / playback
+};
+
+class TrackListModel : public QAbstractTableModel
+{
+    Q_OBJECT
+
+public:
+    enum Column {
+        ColNumber   = 0,
+        ColTitle    = 1,
+        ColArtist   = 2,
+        ColAlbum    = 3,
+        ColDuration = 4,
+        ColCount
+    };
+
+    enum Role {
+        TrackIdRole   = Qt::UserRole + 1,
+        TrackJsonRole = Qt::UserRole + 2,
+        HiResRole     = Qt::UserRole + 3,
+    };
+
+    explicit TrackListModel(QObject *parent = nullptr);
+
+    void setTracks(const QJsonArray &tracks);
+    void clear();
+
+    const TrackItem &trackAt(int row) const { return m_tracks.at(row); }
+    int rowCount(const QModelIndex &parent = {}) const override;
+    int columnCount(const QModelIndex &parent = {}) const override;
+    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
+    QVariant headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const override;
+
+    static QString formatDuration(qint64 secs);
+
+private:
+    QVector<TrackItem> m_tracks;
+};