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/LtsPluginManager/lts_plugin_loader.h

@@ -0,0 +1,94 @@
+/**
+ * @RDE_HEADER@
+ * plugin loader helper function
+ * $Id$
+ * $HeadURL$
+ * $Author$
+ *
+ * Created by Christian Ehrlicher, SLSE, 2016-07-07
+ */
+
+#pragma once
+
+#define PLUGIN_LOADER_VERSION 3
+
+#include <qglobal.h>
+#include <functional>
+#include <QMap>
+#include <QPair>
+
+#ifndef LTSPLUGINLOADER_EXPORT
+# ifdef BUILD_STATIC_LIBRARIES
+#  define LTSPLUGINLOADER_EXPORT
+# else
+#  if defined(MAKE_LTSPLUGINLOADER_LIB)
+#   define LTSPLUGINLOADER_EXPORT Q_DECL_EXPORT
+#  else
+#   define LTSPLUGINLOADER_EXPORT Q_DECL_IMPORT
+#  endif
+# endif
+#endif
+
+class QObject;
+class QPluginLoader;
+
+namespace LtsAppDescriptor
+{
+struct AppDescription;
+}
+
+namespace LtsPluginManager
+{
+
+enum class PluginType
+{
+  UNKNOWN = 0, // should not happen
+  DATA, // 1
+  GUI, // 2
+  TOPIC_TYPE,
+  PROJECT,
+  STYLE,
+  SPECIAL, // TODO: rm
+  GUI_ELEMENT,
+
+};
+
+
+struct PluginInstance // one instance for one plugin
+{
+  QString pluginName;
+  QString fullFileName;
+  QString fileName;
+  QObject *plugin = nullptr;
+  QPluginLoader *pluginLoader = nullptr;
+};
+
+
+class LTSPLUGINLOADER_EXPORT LtsPluginLoader
+{
+public:
+  static LtsPluginLoader *getInstance();
+
+  void unloadAllPlugins();
+
+  void checkPlugins(const QVector<LtsAppDescriptor::AppDescription> &appVector,
+                    QStringList &errors /* out */);
+
+  bool loadPlugins(PluginType requestedPluginType,
+                   const std::function<bool(const PluginInstance &pluginInstance)> &loadPlugin,
+                   const QStringList &requiredPlugins = QStringList(), /* leave empty to get all plugins of the given type */
+                   const QString &specialTopicTypeFilter = QString(),
+                   const QStringList &optionalPlugins = QStringList());
+
+  typedef QPair<PluginType, QString> PluginKey;
+
+private:
+  friend struct LtsPluginLoaderHandler;
+
+  LtsPluginLoader() = default;
+  ~LtsPluginLoader();
+
+  QMap<PluginKey, PluginInstance> m_loadedPlugins; // TODO: meh...
+};
+
+} // namespace LtsPluginManager