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/main.cpp

@@ -0,0 +1,39 @@
+#include "mainwindow.hpp"
+#include "backend/qobuzbackend.hpp"
+
+#include <QApplication>
+#include <QStyleFactory>
+
+int main(int argc, char *argv[])
+{
+    QApplication app(argc, argv);
+    app.setApplicationName(QStringLiteral("qobuz-qt"));
+    app.setOrganizationName(QStringLiteral("qobuz-qt"));
+    app.setApplicationVersion(QStringLiteral("0.1.0"));
+
+    // Dark palette consistent with spotify-qt style
+    app.setStyle(QStyleFactory::create(QStringLiteral("Fusion")));
+    QPalette darkPalette;
+    darkPalette.setColor(QPalette::Window,          QColor(35, 35, 35));
+    darkPalette.setColor(QPalette::WindowText,      Qt::white);
+    darkPalette.setColor(QPalette::Base,            QColor(25, 25, 25));
+    darkPalette.setColor(QPalette::AlternateBase,   QColor(45, 45, 45));
+    darkPalette.setColor(QPalette::ToolTipBase,     Qt::white);
+    darkPalette.setColor(QPalette::ToolTipText,     Qt::white);
+    darkPalette.setColor(QPalette::Text,            Qt::white);
+    darkPalette.setColor(QPalette::Button,          QColor(53, 53, 53));
+    darkPalette.setColor(QPalette::ButtonText,      Qt::white);
+    darkPalette.setColor(QPalette::BrightText,      Qt::red);
+    darkPalette.setColor(QPalette::Link,            QColor(42, 130, 218));
+    darkPalette.setColor(QPalette::Highlight,       QColor(42, 130, 218));
+    darkPalette.setColor(QPalette::HighlightedText, Qt::black);
+    darkPalette.setColor(QPalette::Disabled, QPalette::Text,       QColor(127, 127, 127));
+    darkPalette.setColor(QPalette::Disabled, QPalette::ButtonText, QColor(127, 127, 127));
+    app.setPalette(darkPalette);
+
+    auto *backend = new QobuzBackend;
+    MainWindow window(backend);
+    window.show();
+
+    return app.exec();
+}