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/LtsWebSocket/client_connection.h

@@ -0,0 +1,91 @@
+/**
+  * @RDE_HEADER@
+  * The ClientConnection class represents a connection to a single client.
+  * $Id$
+  * $HeadURL$
+  * $Author$
+  * Created by Hannes Baeuerle, SLSE, 2016-08-25
+  */
+#pragma once
+
+#include <QtCore/QThread>
+#include <QtCore/QQueue>
+
+#include "reply_message.h"
+#include "logger.h"
+#include <LtsWebSocket/ltswebsocketserver_export.h>
+
+class QWebSocket;
+
+namespace LtsWebSocket
+{
+
+/**
+ * @brief The ClientConnection class represents a connection to a single client
+ */
+class LTSWEBSOCKETSERVER_EXPORT ClientConnection
+  : public QThread
+  , public ReplyHandler
+{
+  Q_OBJECT
+public:
+  /**
+   * @brief ClientConnection Constructor
+   * @param socket Pointer to a QWebSocket Object. Should be QWebSocketServer::nextPendingConnection()
+   * @param parent QObject parent
+   */
+  explicit ClientConnection(QWebSocket *socket, QObject *parent = nullptr);
+
+
+  /**
+   * @brief ~ClientConnection Destructor
+   */
+  ~ClientConnection();
+
+  /**
+   * @brief init Initialises the ClientConnection
+   * @return True on success, otherwise false
+   */
+  bool init();
+
+  /**
+   * @brief writeTextMessage Add a message to a queue to be sent to the client
+   * @param message Message which is queued
+   */
+  void addReply(ReplyMessage *message) override;
+
+  QWebSocket *webSocket() { return m_socket; }
+signals:
+  /**
+   * @brief newTextMessage Emitted when a new text message arrives at the associated socket
+   * @param message The new message
+   */
+  void newTextMessage(ClientConnection *client, const QString &message);
+
+  /**
+   * @brief disconnected Emitted when a client disconnects
+   * @param client The client
+   */
+  void disconnected(ClientConnection *client);
+
+
+private slots:
+  void onNewTextMessageFromSocket(const QString &message);
+  void sendMessagesFromQueue();
+  void onSocketDisconnect();
+private: // methods
+  /**
+   * @brief sendMessages Runs in an own thread and constantly tries to send
+   * queued messages
+   */
+  void sendMessages();
+
+private: // attributes
+  QWebSocket *m_socket;
+  QQueue<ReplyMessage *> m_messageQueue;
+
+  LOGGER_T m_logger;
+
+
+}; // class ClientConnection
+} // namespace LtsWebSocket