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>

qt5-before/dlbo/Lts/Common/PluginInterfaces/gui_plugin_interface.h

@@ -0,0 +1,105 @@
+/**
+  * @RDE_HEADER@
+  * Interface for HMI plugins
+  * $Id$
+  * $HeadURL$
+  * $Author$
+  * Created by Christian Ehrlicher, SLSE, 2016-02-29
+  */
+
+#pragma once
+
+#include <LtsWidgets/lts_base.h>
+#include <ProjectConfig/project_defines.h>
+#include <LtsAppDescriptor/lts_app_descriptor.h>
+#include <LtsUtilsCore/lts_translatable_identifier.h>
+
+#include <QObject>
+#include <QVector>
+#include <QFlags>
+#include <memory>
+
+
+namespace NGL
+{
+class INGLLogger;
+}
+
+namespace LtsWidgets
+{
+class LtsBackgroundWidget;
+class LtsBaseLayoutWidget;
+}
+namespace LtsSession
+{
+class LtsSession;
+}
+
+namespace GuiPluginBase
+{
+class Interface;
+
+
+class Plugin // one instance per plugin
+{
+public:
+  Plugin() = default;
+  virtual ~Plugin() = default;
+
+  virtual QString pluginName() = 0;
+  virtual std::shared_ptr<Interface> createGuiInterface(LtsSession::LtsSession *session) = 0;
+  virtual bool availableInPartition(IDL::PartitionType partition) const = 0;
+};
+
+
+// per session
+class Interface
+{
+public:
+  Interface(LtsSession::LtsSession *session, NGL::INGLLogger &logger)
+    : m_hasInit(true)
+    , m_session(session)
+    , m_logger(logger)
+    , m_appId(LtsAppDescriptor::App::Login)
+  {}
+  virtual ~Interface() = default;
+
+  void setFlags(const QFlags<LtsAppDescriptor::PluginInfo::Flag> &flags) { m_flags = flags; }
+  const QFlags<LtsAppDescriptor::PluginInfo::Flag> &getFlags() const { return m_flags; }
+  void setOptions(const QStringList &options) { m_options = options; }
+  const QStringList &getOptions() const { return m_options; }
+  void setAppId(LtsAppDescriptor::App appId) { m_appId = appId; }
+  LtsAppDescriptor::App appId() const { return m_appId; }
+
+  virtual QVector<LtsWidgets::PluginData> getActions() { return QVector<LtsWidgets::PluginData>(); } // only override when default behaviour unwanted or insufficient (when menu items are necessary)
+  
+  virtual bool fetchInterfaces() { return true; } // only override when default behaviour unwanted or insufficient (if foreign interfaces must be fetched)
+  virtual void clearInterfaces() {} // only override when default behaviour unwanted or insufficient (if foreign interfaces were fetched)
+  virtual QString menuGroup() const { return {}; }
+  virtual LtsUtils::LtsTranslatableIdentifier menuGroupIdentifier() const { m_hasMenuGroupIdentifier = false; return {}; }
+  virtual bool availableInPartition(IDL::PartitionType partition) const { Q_UNUSED(partition); return true; } // FIXME: remove !
+  virtual void init() { m_hasInit = false; } // called before payloads - needs to be quit with signalInitDone(); !
+
+  // NOTE: parameter 'mainBackground' is deprecated!
+  virtual void executePayload(LtsWidgets::LtsBackgroundWidget *mainBackground) { (void)mainBackground; } // must be overridden when executionPriority was overridden
+  virtual int executionPriority() const { return -1; } // only override when default behaviour unwanted or insufficient [smaller = executed sooner, 0 = first, 9999 = unpriorized - see docs!]
+
+  //virtual std::shared_ptr<ForeignDataInterface> getForeignDataInterface() = 0;
+
+  bool m_hasInit;
+  mutable bool m_hasMenuGroupIdentifier = true;
+
+protected:
+  LtsSession::LtsSession *m_session;
+  NGL::INGLLogger &m_logger;
+
+private:
+  QFlags<LtsAppDescriptor::PluginInfo::Flag> m_flags;
+  QStringList m_options;
+  LtsAppDescriptor::App m_appId;
+  //std::shared_ptr<ForeignDataInterface> m_foreignInterface;
+};
+
+} // namespace GuiPluginBase
+
+Q_DECLARE_INTERFACE(GuiPluginBase::Plugin, "gui")