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.cpp

@@ -0,0 +1,95 @@
+/**
+  * @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
+  */
+#include "connection_handler.h"
+
+#include "client_connection.h"
+
+#include <QtWebSockets/QWebSocket>
+
+using namespace LtsWebSocket;
+
+ConnectionHandler::ConnectionHandler(QObject *parent)
+  : QObject(parent)
+  , m_server(nullptr)
+  , m_logger(getLogger("ConnectionHandler"))
+{}
+
+ConnectionHandler::~ConnectionHandler()
+{
+  for (auto connection : qAsConst(m_connections))
+    connection->disconnect(this);
+}
+
+bool ConnectionHandler::init(const QString &serviceName, unsigned short port)
+{
+  if (m_server != nullptr)
+  {
+    m_server->disconnect();
+    delete m_server;
+  }
+  // TODO: get the SslMode from config ?
+  m_server = new QWebSocketServer(QStringLiteral("RME-") + serviceName, QWebSocketServer::NonSecureMode, this);
+
+  connect(m_server, &QWebSocketServer::newConnection, this, &ConnectionHandler::onNewConnection);
+  connect(m_server, &QWebSocketServer::serverError, this, &ConnectionHandler::onServerError);
+
+  DEBUG_LOG(m_logger) << "Trying to listen ";
+  if (!m_server->listen(QHostAddress::Any, port))
+  {
+    ERROR_LOG(m_logger) << "Not possible to listen to port " << port;
+    return false;
+  }
+  DEBUG_LOG(m_logger) << "... ok, port " << m_server->serverPort();
+
+  return true;
+}
+
+void ConnectionHandler::sendToAllClients(ReplyMessage *message)
+{
+  for (auto connection : qAsConst(m_connections))
+    connection->addReply(new ReplyMessage(*message));
+
+  delete message;
+}
+
+void ConnectionHandler::onServerError(QWebSocketProtocol::CloseCode closeCode)
+{
+  ERROR_LOG(m_logger) << "Got server error with close code " << closeCode;
+}
+
+void ConnectionHandler::onNewConnection()
+{
+  while (m_server->hasPendingConnections())
+  {
+    QWebSocket *socket = m_server->nextPendingConnection();
+
+    ClientConnection *newConnection = new ClientConnection(socket, this);
+    connect(newConnection, &ClientConnection::destroyed, this, [this](QObject* o)
+    {
+      m_connections.remove(static_cast<ClientConnection*>(o));
+    });
+
+    if (!newConnection->init())
+    {
+      ERROR_LOG(m_logger) << "Failed to initialise new client";
+      delete newConnection;
+      newConnection = nullptr;
+      continue;
+    }
+    newConnection->start();
+
+    connect(newConnection, &ClientConnection::newTextMessage, this, &ConnectionHandler::newTextMessageFromClient);
+    connect(newConnection, &ClientConnection::disconnected, this, &ConnectionHandler::clientDisconnected);
+    connect(newConnection, &ClientConnection::finished, newConnection, &ClientConnection::deleteLater);
+
+    m_connections.insert(newConnection);
+    emit clientConnected(newConnection);
+    INFO_LOG(m_logger) << "New client connected ip: " << socket->localAddress().toString() << ":" << socket->localPort();
+  }
+}