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/connection_handler.h

@@ -0,0 +1,88 @@
+/**
+  * @RDE_HEADER@
+  * The ConnectionHandler class functions as a WebSocket server and manages incoming client connections.
+  * $Id$
+  * $HeadURL$
+  * $Author$
+  * Created by Hannes Baeuerle, SLSE, 2016-08-25
+  */
+#pragma once
+
+#include <QtNetwork/QHostAddress>
+#include <QtWebSockets/qwebsocketprotocol.h>
+#include <QtWebSockets/QWebSocketServer>
+
+#include "logger.h"
+
+namespace LtsWebSocket
+{
+class MessageHandler;
+class ClientConnection;
+class ReplyMessage;
+
+/**
+ * @brief The ConnectionHandler class functions as a WebSocket server and manages incoming client connections
+ */
+class ConnectionHandler
+  : public QObject
+{
+  Q_OBJECT
+public:
+  /**
+   * @brief ConnectionHandler
+   * @param parent
+   */
+  explicit ConnectionHandler(QObject *parent = nullptr);
+  ~ConnectionHandler();
+
+  /**
+   * @brief init Starts listening for incoming connections and connects internal signals and slots
+   * @param serviceName Is Used to name the server (RDE-"servicename")
+   * @param port Port the server is listening, if 0 the port number will be random
+   * @return True on success, otherwise false
+   */
+  bool init(const QString &serviceName, unsigned short port);
+
+  /**
+   * @brief sendToAll Sends the given msg to all connected Clients
+   * @param message Message to be send
+   */
+  void sendToAllClients(ReplyMessage *message);
+
+  /**
+   * @brief webSocketPort returns the listen port
+   * @return listen port
+   */
+  unsigned short webSocketPort() { return m_server->serverPort(); }
+
+signals:
+  /**
+   * @brief newTextMessageFromClient Emitted when a message from any client is received
+   * @param client Client where replies are written to
+   * @param message Message from the client
+   */
+  void newTextMessageFromClient(ClientConnection *client, const QString &message);
+
+  /**
+   * @brief clientDisconnected Emitted when a client disconnects
+   * @param client The client
+   */
+  void clientDisconnected(ClientConnection *client);
+
+  /**
+   * @brief clientConnected Emitted when a client connects
+   * @param client The client
+   */
+  void clientConnected(ClientConnection *client);
+
+private slots:
+  void onServerError(QWebSocketProtocol::CloseCode closeCode);
+  void onNewConnection();
+
+private: // attributes
+  QWebSocketServer *m_server;
+  QSet<ClientConnection *> m_connections;
+  LOGGER_T m_logger;
+
+};
+} // namespace LtsWebSocket