Use QCoreApplication for the race test, set QT_QPA_PLATFORM=offscreen
and QT_MEDIA_BACKEND=ffmpeg for playback tests, and export the same vars
in CI before ctest to avoid subprocess aborts without a display.
- Correct history/resume next-previous context and list index resync after reload
- Abort stale RadioBrowser requests and suppress error banners when cache satisfies loads
- Reset local search filter on page changes and debounce compact-mode API search
- Move system tray to C++ (QSystemTrayIcon) for reliable Wayland context menus
- Harden MPRIS registration and metadata updates for Plasma media widgets
- Add playback and API race unit tests
- Drop unused KF6 Kirigami, I18n, and CoreAddons build dependencies
- Update packaging docs, CI, and PKGBUILD to match Qt-only requirements
