Kiosk: add a data-driven System Settings menu

Settings now shows Proclamations, Audio Options, System Settings, System
Logs, and Back. The new SystemSettingsPage groups Email Address, License
Key, WiFi Setup, Time Zone Setup, and Date Format, driven by the pure
settings::systemSettingEntries() list so future entries need one row, not
new menu plumbing. Adds unit tests for the entry list.

CMakeLists.txt

@@ -40,6 +40,8 @@ add_executable(radiantwave
     src/page_manager.cpp
     src/home.cpp
     src/settings.cpp
+    src/settings_menu.cpp
+    src/system_settings_page.cpp
     src/wifi_setup_page.cpp
     src/audio_settings_page.cpp
     src/audio/audio_manager.cpp
@@ -226,6 +228,14 @@ add_executable(test_date_format
 target_include_directories(test_date_format PRIVATE src)
 target_link_libraries(test_date_format PRIVATE GTest::gtest_main)
 
+# System Settings menu entry list (pure data, no SDL linkage)
+add_executable(test_settings_menu
+    tests/test_settings_menu.cpp
+    src/settings_menu.cpp
+)
+target_include_directories(test_settings_menu PRIVATE src)
+target_link_libraries(test_settings_menu PRIVATE GTest::gtest_main)
+
 # TimeZone unit tests
 add_executable(test_timezone
     tests/test_timezone.cpp