feat: dual time zones, autostart, tray icon, config relocation, tests

- Dual clock (primary/secondary time zone) with IANA picker, persisted in XML
- AutoStartManager: macOS LaunchAgent (com.clouck.clock, RunAtLoad)
- Tray icon: template image, light/dark adaptation, toggle + quit menu
- ConfigManager: default path moved to QStandardPaths::AppConfigLocation
- Qt Test suite (ConfigManager, AutoStartManager) wired into CTest
- GitHub origin renamed to upstream; private Gitea repo as origin

.gitignore

@@ -91,3 +91,9 @@ Icon
 *.dmg
 build
 test*
+!tests/
+!tests/*.cpp
+
+# AW
+.aw/
+CLAUDE.md