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/CMakeLists.txt

@@ -0,0 +1,44 @@
+target_sources(qobuz-qt PRIVATE
+    # Entry point
+    main.cpp
+
+    # Main window
+    mainwindow.hpp
+    mainwindow.cpp
+
+    # Backend (Qt wrapper around Rust FFI)
+    backend/qobuzbackend.hpp
+    backend/qobuzbackend.cpp
+
+    # Views
+    view/maintoolbar.hpp
+    view/maintoolbar.cpp
+    view/maincontent.hpp
+    view/maincontent.cpp
+    view/sidepanel/view.hpp
+    view/sidepanel/view.cpp
+
+    # Lists
+    list/tracks.hpp
+    list/tracks.cpp
+    list/library.hpp
+    list/library.cpp
+
+    # Models
+    model/tracklistmodel.hpp
+    model/tracklistmodel.cpp
+
+    # Dialogs
+    dialog/login.hpp
+    dialog/login.cpp
+    dialog/settings.hpp
+    dialog/settings.cpp
+
+    # Widgets (header-only)
+    widget/clickableslider.hpp
+    widget/volumebutton.hpp
+
+    # Utils (header-only)
+    util/icon.hpp
+    util/settings.hpp
+)