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

build_cross_platform.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
-# Cross-platform build script for Clouck
+# Cross-platform build script for DualFloatingClock
 
-echo "Building Clouck - Cross-platform Clock Application"
+echo "Building DualFloatingClock - Cross-platform Clock Application"
 echo "=================================================="
 
 # Detect operating system
@@ -49,19 +49,19 @@ echo ""
 echo "Executable location:"
 
 if [ "$OS" == "macOS" ]; then
-    echo "  - build/Clouck.app/Contents/MacOS/Clouck (macOS)"
+    echo "  - build/DualFloatingClock.app/Contents/MacOS/DualFloatingClock (macOS)"
 elif [ "$OS" == "Windows" ]; then
-    echo "  - build/Release/Clouck.exe (Windows)"
+    echo "  - build/Release/DualFloatingClock.exe (Windows)"
 elif [ "$OS" == "Linux" ]; then
-    echo "  - build/Clouck (Linux)"
+    echo "  - build/DualFloatingClock (Linux)"
 fi
 
 echo ""
 echo "To run the application:"
 if [ "$OS" == "macOS" ]; then
-    echo "  ./build/Clouck.app/Contents/MacOS/Clouck"
+    echo "  ./build/DualFloatingClock.app/Contents/MacOS/DualFloatingClock"
 elif [ "$OS" == "Windows" ]; then
-    echo "  ./build/Release/Clouck.exe"
+    echo "  ./build/Release/DualFloatingClock.exe"
 elif [ "$OS" == "Linux" ]; then
-    echo "  ./build/Clouck"
+    echo "  ./build/DualFloatingClock"
 fi