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/Tools/Examples/gui_element_plugin.cpp

@@ -0,0 +1,60 @@
+#include <Plugins/ParticipantManagement/ppm_data_plugin_interface.h>
+#include <PluginInterfaces/gui_plugin_interface.h>
+#include <LtsSession/lts_session.h>
+
+#include "gui_element_plugin.h"
+#include "custom_widget.h"
+
+
+
+#include <QDebug>
+
+GuiElementPlugin::GuiElementPlugin()
+{
+
+}
+
+QWidget *GuiElementPlugin::createGuiElement(QWidget *parent)
+{
+  m_customWidget = new CustomWidget(parent);
+  if (!m_ppmDtc)
+  {
+    qCritical()<<" ppmDtc not yet init!!!";
+    return nullptr;
+  }
+
+  connect(m_customWidget, &CustomWidget::finOnMapClicked, this, &GuiElementPlugin::onFindOnMap);
+  connect(m_ppmDtc.get(), &ParticipantManagement::Interface::Dtc::participantPositionChanged,
+          m_customWidget, [=](const ParticipantManagement::ParticipantPosition &ppPos){
+        m_customWidget->onPositionChanged(ppPos.pos(), m_participantId);
+  }, Qt::UniqueConnection);
+  m_customWidget->onPositionChanged(m_ppmDtc->participantPosition(m_participantId).pos(), m_participantId);
+  return m_customWidget;
+}
+
+
+bool GuiElementPlugin::init(LtsSession::LtsSession *session, int participantId)
+{
+  m_session  = session;
+
+  if (!m_session->getDtc<ParticipantManagement::DataInterface>(m_ppmDtc))
+  {
+    qCritical()<<"couln't init ppmDtc for gui element ";
+    return false;
+  }
+
+  if (!session->getForeignGuiInterface<SituationMap::ForeignGuiInterface>(m_sitMapGuiIfc))
+  {
+    qCritical()<<"couln't init sitMapGuiIfc for gui element ";
+    return false;
+  }
+
+  m_participantId = participantId;
+  return true;
+}
+
+void GuiElementPlugin::onFindOnMap()
+{
+  if (m_sitMapGuiIfc)
+    m_sitMapGuiIfc->centerMapToParticipant(m_participantId);
+}