Add Lts/Application module with Qt6 CMakeLists updates

- Copy Lts/Application from qt5-before (AarApp, OpApp, THP submodules)
- Update all CMakeLists.txt to use Qt6::Core, Qt6::Widgets, Qt6::Xml, Qt6::Network, Qt6::PrintSupport, Qt6::Svg, Qt6::WebEngineCore, Qt6::WebEngineWidgets
- No SIGNAL/SLOT, QRegExp, QDesktopWidget, or QTextCodec issues found in Application source code
- Module ready for Qt6 build validation

qt6-after/qt6-migrated-legatus/Lts/Application/THP/thpwidgets/thp_pdf_widget.h

@@ -0,0 +1,40 @@
+/**
+  * @RDE_HEADER@
+  * Handle PDF output for thp
+  * $Id$
+  * $HeadURL$
+  * $Author$
+  */
+#pragma once
+#include <QWidget>
+
+
+class QUrl;
+namespace Ui
+{
+class PdfWidget;
+}
+
+namespace THP
+{
+class PdfWidget : public QWidget
+{
+  Q_OBJECT
+public:
+  explicit PdfWidget(QWidget *parent = nullptr);
+  ~PdfWidget();
+
+  bool showPDF(const QUrl &pdf);
+  void setZoomFactor(double newZoomFactor);
+  QVector<QImage> getPrintableImages(int resolution = 300);
+  void resizePdfToWidth();
+
+protected Q_SLOTS:
+  void onPreviousPage();
+  void onNextPage();
+  void pageChanged(int cur, int max);
+protected:
+
+  Ui::PdfWidget *ui;
+};
+} // namespace THP