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

tests/CMakeLists.txt

@@ -0,0 +1,48 @@
+find_package(Qt6 REQUIRED COMPONENTS Test)
+
+set(TEST_SOURCES
+    radiobackend_playback_test.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src/radiobackend.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src/radiostation.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src/radiobrowser.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src/bearplayer.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src/coverartfetcher.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src/icyreader.cpp
+)
+
+add_executable(radiobackend_playback_test ${TEST_SOURCES})
+
+target_include_directories(radiobackend_playback_test PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src
+)
+
+target_link_libraries(radiobackend_playback_test PRIVATE
+    Qt6::Core
+    Qt6::Network
+    Qt6::Test
+    Qt6::Widgets
+    Qt6::Multimedia
+)
+
+add_test(NAME radiobackend_playback_test COMMAND radiobackend_playback_test)
+
+set(RACE_TEST_SOURCES
+    radiobrowser_race_test.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src/radiobrowser.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src/radiostation.cpp
+)
+
+add_executable(radiobrowser_race_test ${RACE_TEST_SOURCES})
+
+target_include_directories(radiobrowser_race_test PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src
+)
+
+target_link_libraries(radiobrowser_race_test PRIVATE
+    Qt6::Core
+    Qt6::Network
+    Qt6::Test
+    Qt6::Widgets
+)
+
+add_test(NAME radiobrowser_race_test COMMAND radiobrowser_race_test)