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

config_manager.cpp

@@ -48,7 +48,8 @@ bool ConfigManager::loadSettings(const QString &filename)
     QXmlStreamReader reader(&file);
 
     // Check if it's a valid XML file
-    if (!reader.readNextStartElement() || reader.name() != QString("ClouckConfig"))
+    if (!reader.readNextStartElement()
+        || (reader.name() != QString("DualFloatingClockConfig") && reader.name() != QString("ClouckConfig")))
     {
         qDebug() << "Invalid config file format";
         file.close();
@@ -159,7 +160,7 @@ bool ConfigManager::saveSettings(const QString &filename)
     writer.writeStartDocument();
 
     // Root element
-    writer.writeStartElement("ClouckConfig");
+    writer.writeStartElement("DualFloatingClockConfig");
 
     // Colors: store #RRGGBB when fully opaque, #AARRGGBB when translucent —
     // the XML stays close to what the user typed.