feat: rename project to DualFloatingClock, add README, public release

- Full rename: CMake target, bundle, LaunchAgent label
  (com.dualfloatingclock.clock), QSettings org/app, tray tooltip,
  icns resource, build scripts, CI workflows, sample config
- Config XML: new root DualFloatingClockConfig; reader accepts legacy
  ClouckConfig root for painless migration of existing settings
- README rewritten: fork provenance (ivaquero/clouck), features, build,
  tests, usage
- Drop stale README-CN.md

main.cpp

@@ -55,16 +55,16 @@ int main(int argc, char *argv[])
     clouck_setActivationPolicyAccessory();
 #endif
 
-    app.setApplicationName("Clouck");
-    app.setOrganizationName("Clouck");
-    app.setApplicationDisplayName("Clouck");
+    app.setApplicationName("DualFloatingClock");
+    app.setOrganizationName("DualFloatingClock");
+    app.setApplicationDisplayName("DualFloatingClock");
 
     ClockWidget clock;
     clock.show();
 
     // Start at Login: honor the persisted choice instead of always forcing it.
     {
-        QSettings autoStartSettings("Clouck", "Clouck");
+        QSettings autoStartSettings("DualFloatingClock", "DualFloatingClock");
         const bool startAtLogin = autoStartSettings.value("startAtLogin", true).toBool();
         if (startAtLogin)
         {
@@ -79,7 +79,7 @@ int main(int argc, char *argv[])
 
     const QStyleHints *styleHints = app.styleHints();
     QSystemTrayIcon trayIcon(createTrayIcon(trayIconColorForScheme(styleHints->colorScheme())), &app);
-    trayIcon.setToolTip("Clouck");
+    trayIcon.setToolTip("DualFloatingClock");
 
     QObject::connect(styleHints, &QStyleHints::colorSchemeChanged, &trayIcon,
                      [&trayIcon](Qt::ColorScheme scheme) {
@@ -91,12 +91,12 @@ int main(int argc, char *argv[])
 
     QAction *startAtLoginAction = trayMenu.addAction("Start at Login");
     {
-        QSettings autoStartSettings("Clouck", "Clouck");
+        QSettings autoStartSettings("DualFloatingClock", "DualFloatingClock");
         startAtLoginAction->setCheckable(true);
         startAtLoginAction->setChecked(autoStartSettings.value("startAtLogin", true).toBool());
     }
     QObject::connect(startAtLoginAction, &QAction::toggled, &app, [](bool checked) {
-        QSettings autoStartSettings("Clouck", "Clouck");
+        QSettings autoStartSettings("DualFloatingClock", "DualFloatingClock");
         autoStartSettings.setValue("startAtLogin", checked);
         if (checked)
         {