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/CMakeLists.txt

@@ -6,6 +6,9 @@ target_sources(qobuz-qt PRIVATE
     mainwindow.hpp
     mainwindow.cpp
 
+    # Queue (header-only)
+    playqueue.hpp
+
     # Backend (Qt wrapper around Rust FFI)
     backend/qobuzbackend.hpp
     backend/qobuzbackend.cpp
@@ -15,6 +18,10 @@ target_sources(qobuz-qt PRIVATE
     view/maintoolbar.cpp
     view/maincontent.hpp
     view/maincontent.cpp
+    view/context/view.hpp
+    view/context/view.cpp
+    view/queuepanel.hpp
+    view/queuepanel.cpp
     view/sidepanel/view.hpp
     view/sidepanel/view.cpp