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/LtsProjectionWorkstation/WebSocket/messages.h

@@ -0,0 +1,197 @@
+/**
+  * @RDE_HEADER@
+  * LtsProjectionWorkstation Messages & Factory
+  * $Id$
+  * $HeadURL$
+  * $Author$
+  */
+
+#pragma once
+
+#include "json_keys.h"
+
+#include <LtsWebSocket/json_keys.h>
+#include <LtsWebSocket/client_message.h>
+
+#include <LtsProjectionWorkstation/lts_projection_workstation_export.h>
+#include <LtsProjectionWorkstation/vnc_server_manager.h>
+
+#include <QVector>
+
+namespace LtsWebSocket { class ReplyHandler; }
+
+namespace LtsProjectionWorkstation
+{
+
+class AbstractMessageHandler
+{
+public:
+  virtual ~AbstractMessageHandler() = default;
+  virtual void handleMessage(LtsWebSocket::AbstractClientMessage *message) = 0;
+};
+
+
+class Reply : public LtsWebSocket::ReplyMessage
+{
+public:
+  Reply(const QString &type, const int typeId, const QString &uuid, const QJsonObject &data)
+    : LtsWebSocket::ReplyMessage(type, typeId, uuid)
+  {
+    m_jsonRepresentation.insert(LtsWebSocket::JsonKeys::DATA(), data);
+  }
+};
+
+
+class Message : public LtsWebSocket::AbstractClientMessage
+{
+public:
+  Message(AbstractMessageHandler *handler, LtsWebSocket::ReplyHandler *client, const QString &type, const QString &uuid, const QJsonValue &data = QJsonValue())
+    : LtsWebSocket::AbstractClientMessage(client, type, 1, uuid, data) // Todo: Check whether 1 is feasible
+    , m_handler(handler)
+  {}
+
+  LtsWebSocket::ReplyMessage *toReplyMessage() const
+  {
+    if (!m_handler || !m_client)
+      return new Reply(m_type, m_typeId, m_uuid, m_replyData.toObject());
+    return nullptr;
+  }
+
+  void addReply(LtsWebSocket::ReplyMessage *reply)
+  {
+    if (m_client)
+      m_client->addReply(reply);
+  }
+
+protected:
+  AbstractMessageHandler *m_handler;
+  QJsonValue m_replyData;
+
+}; //Message
+
+
+class LTSPROJECTIONWORKSTATION_EXPORT ErrorMessage : public Message
+{
+public:
+  using Message::Message;
+  ErrorMessage(const QString &uuid, const QString &reason);
+
+  // AbstractClientMessage interface
+  void process() override final;
+  bool hasValidData() const override final;
+
+private:
+  QString m_reason;
+};
+
+namespace STC // Server -> Client
+{
+
+class LTSPROJECTIONWORKSTATION_EXPORT LoginRequestReply : public Message
+{
+public:
+  enum Reason
+  {
+    LoginSuccessful,
+    OtherUser,
+  };
+
+  using Message::Message;
+  LoginRequestReply(const QString &uuid, Reason reason, int reasonUserId, const QVector<VncScreen> &screens);
+
+  // AbstractClientMessage interface
+  void process() override final;
+  bool hasValidData() const override final;
+
+  int reasonUserId() const { return m_reasonUserId; }
+  Reason reason() const    { return m_reason; }
+  const QVector<VncScreen> &screens() const { return m_screens; }
+
+private:
+  QVector<VncScreen> m_screens;
+  int    m_reasonUserId = -1;
+  Reason m_reason = LoginSuccessful;
+}; // LoginReply
+
+class LTSPROJECTIONWORKSTATION_EXPORT DedicatedDisconnect : public Message
+{
+public:
+  using Message::Message;
+  DedicatedDisconnect(const QString &uuid, int userId);
+
+  // AbstractClientMessage interface
+  void process() override final;
+  bool hasValidData() const override final;
+
+  int userid() const { return m_userId; }
+
+private:
+  int m_userId = -1;
+
+}; // DedicatedDisconnect
+
+
+} // namespace STC
+
+
+namespace CTS // Client -> Server
+{
+
+class LTSPROJECTIONWORKSTATION_EXPORT LoginRequest : public Message
+{
+public:
+  using Message::Message;
+  LoginRequest(const QString &uuid, int userId, int priority, int exerciseId, const QByteArray &settingsData);
+
+  // AbstractClientMessage interface
+  void process() override final;
+  bool hasValidData() const override final;
+
+  int userId() const { return m_userId; }
+  int priority() const { return m_priority; }
+  int exerciseId() const { return m_exerciseId; }
+  const QByteArray &settingsData() const { return m_settingsData; }
+
+private:
+  QByteArray m_settingsData;
+  int m_userId = 0;
+  int m_priority = 0;
+  int m_exerciseId = 0;
+
+}; // LoginRequest
+
+
+class LTSPROJECTIONWORKSTATION_EXPORT LogoutRequest : public Message
+{
+public:
+  using Message::Message;
+  explicit LogoutRequest(const QString &uuid)
+    : Message(nullptr, nullptr, JsonKeys::LOGOUT_REQUEST(), uuid, QJsonValue())
+  {}
+
+  // AbstractClientMessage interface
+  void process() override final;
+  bool hasValidData() const override final;
+
+}; // LogoutRequest
+
+
+class LTSPROJECTIONWORKSTATION_EXPORT DisconnectRequest : public Message
+{
+public:
+  using Message::Message;
+  explicit DisconnectRequest(const QString &uuid, int userId);
+
+  // AbstractClientMessage interface
+  void process() override final;
+  bool hasValidData() const override final;
+
+  int userId() const { return m_userId; }
+private:
+  int m_userId{0};
+
+}; // DisconnectRequest
+
+} // namespace CTS
+
+} // LtsProjectionWorkstation