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

DualFloatingClock.pro

@@ -0,0 +1,47 @@
+# Created by and for Qt Creator This file was created for editing the project sources only.
+# You may attempt to use it for building too, by modifying this file here.
+
+TARGET = DualFloatingClock
+
+QT = core gui widgets
+
+SOURCES = \
+   $$PWD/main.cpp \
+   $$PWD/clock_widget.cpp \
+   $$PWD/config_manager.cpp \
+   $$PWD/window_helper.cpp
+
+HEADERS = \
+   $$PWD/clock_widget.h \
+   $$PWD/config_manager.h \
+   $$PWD/window_helper.h \
+   $$PWD/window_helper_macos.h \
+   $$PWD/window_helper_windows.h \
+   $$PWD/window_helper_linux.h
+
+macx {
+   OBJECTIVE_SOURCES = $$PWD/window_helper_macos.mm
+   LIBS += -framework AppKit -framework CoreGraphics
+   QMAKE_CXXFLAGS += -x objective-c++
+}
+
+win32 {
+   SOURCES += $$PWD/window_helper_windows.cpp
+   LIBS += -luser32 -ldwmapi -luser32 -lgdi32 -lkernel32
+}
+
+unix:!macx {
+   LIBS += -lX11 -lXfixes
+}
+
+INCLUDEPATH = \
+    $$PWD/.
+
+# Set build output directories
+DESTDIR = $$PWD/build
+OBJECTS_DIR = $$PWD/build
+MOC_DIR = $$PWD/build
+RCC_DIR = $$PWD/build
+UI_DIR = $$PWD/build
+
+#DEFINES =