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.cpp

@@ -0,0 +1,67 @@
+/**
+  * @RDE_HEADER@
+  * Handle PDF output for thp
+  * $Id$
+  * $HeadURL$
+  * $Author$
+  */
+#include "thp_pdf_widget.h"
+#include "ui_thp_pdf_widget.h"
+
+namespace THP
+{
+
+PdfWidget::PdfWidget(QWidget *parent)
+  : QWidget(parent)
+  , ui(new Ui::PdfWidget)
+{
+  ui->setupUi(this);
+
+  connect(ui->previousPage, &QToolButton::clicked, this, &PdfWidget::onPreviousPage);
+  connect(ui->nextPage,     &QToolButton::clicked, this, &PdfWidget::onNextPage);
+  connect(ui->pdfDocument,  &NGL::PDFDocument::currentPageChanged, this, &PdfWidget::pageChanged);
+}
+
+PdfWidget::~PdfWidget()
+{
+  delete ui;
+}
+
+bool PdfWidget::showPDF(const QUrl &pdf)
+{
+  return ui->pdfDocument->showPDF(pdf);
+}
+
+void PdfWidget::setZoomFactor(double newZoomFactor)
+{
+  ui->pdfDocument->setZoomFactor(newZoomFactor);
+}
+
+void PdfWidget::onPreviousPage()
+{
+  ui->pdfDocument->previousPage();
+}
+
+void PdfWidget::onNextPage()
+{
+  ui->pdfDocument->nextPage();
+}
+
+QVector<QImage> PdfWidget::getPrintableImages(int resolution)
+{
+  return ui->pdfDocument->getPrintableImages(resolution);
+}
+
+void PdfWidget::resizePdfToWidth()
+{
+  ui->pdfDocument->resizePdfToWidth();
+}
+
+void PdfWidget::pageChanged(int cur, int max)
+{
+  ui->pageLabel->setText(tr("Page %1 of %2").arg(cur).arg(max));
+  ui->nextPage->setEnabled(cur < max);
+  ui->previousPage->setEnabled(cur > 1);
+}
+
+}  // namespace THP