Qt6 Migration: Complete migration with DDS/RTI support and build validation

Major Changes:
- Merged latest Qt5 devel content from dlbo (292 files changed, 7 new dirs)
- Consolidated forward-declarations and include folders
- Removed unneeded modules per Niklas' repo check list

Build System Fixes:
- Fixed CMake VERSION_GREATER syntax in ParticipantManagement/CMakeLists.txt
- Added VLC packages (libvlc-dev, vlc-plugin-base) to docker_build.sh
- Added PostgreSQL dev packages (libpq-dev, postgresql-server-dev-all) to Dockerfile
- Fixed locale warnings (ANSI_X3.4-1968 → C.UTF-8)
- Fixed ArcGIS SDK path warnings when BUILD_ARCGIS=OFF

Code Generation Fixes:
- Fixed IDL enum collisions (PortType→CorePortType/DdsutPortType, PdmEventType)
- Fixed Grantlee template svc_translation.cpp.grantlee:
  - Changed {{ idl_enum.name }}_def:: to {{ idl_enum.name }}::
  - Fixed .underlying() calls for C++11 scoped enums (enum class)
- Removed generated files from repo (moc_*, *_dtc.h, *_ftc.h)

Validation:
- BUILD_RTI=ON: SUCCESS
- BUILD_RTI=OFF: SUCCESS
- C++17 standard maintained for RTI 7.7 compatibility
- Ubuntu 26.04 Docker environment verified

Remaining Warnings (expected):
- BgViewer, KDChart, KDReports, Poppler-Qt6 not found (optional features)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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