Major port Qt4 to Qt6

- Updated header inclusions from QtGui to QtWidgets for consistency and compatibility with Qt 5 and later.
- Replaced deprecated QApplication::desktop() with QApplication::primaryScreen() for obtaining screen DPI.
- Modified MyOutputHandler to use QMessageLogContext and QString for improved logging.
- Changed QMatrix to QTransform for image rotation in ImageCutout class.
- Updated various debug statements to use toLocal8Bit() instead of toAscii() for better string handling.
- Refactored several classes to use QElapsedTimer instead of QTime for performance measurement.
- Ensured all operator overloads in Section and Tag classes are marked as const for better const-correctness.

ClippingStation/imagecutout.cpp

@@ -211,7 +211,7 @@ QImage ImageCutout::createCutout() const
     {
         // after calculating the pixmap, we rotate it if needed
         QImage image = px.toImage();
-        QMatrix mx;
+        QTransform mx;
         mx = mx.rotate(m_rotationAngle);
         //  mx = mx.scale(.5, .5);  //dont do this
         image = image.transformed(mx);