Qt6 migration: Fix BUILD_RTI=OFF build errors in TrainingAreaBase

- training_area_telegrams.cpp: Fixed QJsonObject initializer syntax (Qt6 requires {{}} not ({}))
- training_area_telegrams.cpp: Fixed fromJson() methods to access m_* members directly
- training_area_telegrams.cpp: Fixed brace mismatches in multiple toJson() methods
- training_area_telegrams.h: Changed Header struct to public members for consistency
- tx_mixin.cpp: Fixed getEquipmentNumber() template for direct member access
- lts_coordinate.cpp: Added missing #include <iomanip>
- MIGRATION_STATUS.md: Added migration progress tracking document

C++17 constraint enforced due to RTI Connext DDS 7.7.0 incompatibility with C++20+

Build status: BUILD_RTI=OFF successful (0 errors, warnings only)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

qt6-after/qt6-migrated-legatus/Lts/Plugins/NotificationManagement/Gui/NotificationEdit/nom_dialog.cpp

@@ -6,7 +6,7 @@
 
 #include "nom_dialog_model.h"
 
-#include <QLabel>
+#include <QtWidgets/QLabel>
 #include <QTextBrowser>
 #include <LtsSession/lts_session.h>
 #include <LtsSession/lts_session_data.h>

qt6-after/qt6-migrated-legatus/Lts/Plugins/NotificationManagement/Gui/NotificationEdit/nom_dialog_model.cpp

@@ -10,7 +10,7 @@
 #include <NotificationManagement/nom_translation.h>
 #include <OperatorManagement/opm_data_plugin_interface.h>
 
-#include <QCoreApplication>
+#include <QtCore/QCoreApplication>
 
 
 namespace NotificationManagement

qt6-after/qt6-migrated-legatus/Lts/Plugins/NotificationManagement/Gui/NotificationEdit/nom_edit_gui_plugin.cpp

@@ -12,10 +12,10 @@
 #include <NotificationManagement/nom_dtc.h>
 #include <Services/AreaEffectSimulation/aes_operator_rights.h>
 
-#include <QApplication>
-#include <QDebug>
-#include <QRegularExpression>
-#include <QRegularExpressionMatch>
+#include <QtWidgets/QApplication>
+#include <QtCore/QDebug>
+#include <QtCore/QRegularExpression>
+#include <QtCore/QRegularExpressionMatch>
 
 namespace NotificationManagement
 {