fix(qt): restore window lifecycle and improve grid artwork

Restore tray-aware close and quit confirmation, circular label covers, and missing label artist portraits. Publish artwork progressively, preload two grid rows, and skip redundant motion reports while preserving data refreshes.

Include regression tests and isolated artwork benchmarks. Verified Linux build, QML checks, and scrolling smoke tests.

cx

crates/qbz-qt/build.rs

@@ -399,6 +399,8 @@ fn build_rhi_items() {
     cc.file("cxx/qt_vulkan_probe.cpp");
     println!("cargo:rerun-if-changed=cxx/win_shell.cpp");
     cc.file("cxx/win_shell.cpp");
+    println!("cargo:rerun-if-changed=cxx/app_lifecycle.cpp");
+    cc.file("cxx/app_lifecycle.cpp");
     // Shell_NotifyIconW tray. No Q_OBJECT, so no moc; the body is inside
     // `#ifdef _WIN32` and compiles to nothing on Linux and macOS.
     println!("cargo:rerun-if-changed=cxx/win_tray.cpp");