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/util/icon.hpp

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <QIcon>
+#include <QString>
+
+namespace Icon
+{
+    inline QIcon get(const QString &name)
+    {
+        // Try theme icon first, fall back to resource
+        if (QIcon::hasThemeIcon(name))
+            return QIcon::fromTheme(name);
+        return QIcon(QStringLiteral(":/icons/%1.svg").arg(name));
+    }
+
+    // Convenient aliases for common icons used throughout the app
+    inline QIcon play()       { return get("media-playback-start"); }
+    inline QIcon pause()      { return get("media-playback-pause"); }
+    inline QIcon stop()       { return get("media-playback-stop"); }
+    inline QIcon next()       { return get("media-skip-forward"); }
+    inline QIcon previous()   { return get("media-skip-backward"); }
+    inline QIcon shuffle()    { return get("media-playlist-shuffle"); }
+    inline QIcon repeat()     { return get("media-playlist-repeat"); }
+    inline QIcon volumeHigh() { return get("audio-volume-high"); }
+    inline QIcon volumeMid()  { return get("audio-volume-medium"); }
+    inline QIcon volumeMute() { return get("audio-volume-muted"); }
+    inline QIcon search()     { return get("edit-find"); }
+    inline QIcon heart()      { return get("emblem-favorite"); }
+    inline QIcon album()      { return get("media-optical"); }
+    inline QIcon artist()     { return get("system-users"); }
+    inline QIcon playlist()   { return get("view-list-symbolic"); }
+}