Fix playback, API races, tray, MPRIS, and search UX; add tests

- 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

.github/workflows/build.yml

@@ -27,14 +27,10 @@ jobs:
               pacman -S --noconfirm --needed \
                 base-devel \
                 cmake \
-                extra-cmake-modules \
                 git \
                 qt6-base \
                 qt6-declarative \
                 qt6-tools \
-                kirigami \
-                kcoreaddons \
-                ki18n \
                 qt6-multimedia \
                 qt6-multimedia-ffmpeg
               cmake -S . -B build -DCMAKE_BUILD_TYPE=Release