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/Common/LtsWidgets/lts_dialog.cpp

@@ -15,33 +15,33 @@
 #include "lts_date_time_edit.h"
 #include "ui_requirement.h"
 
-#include <QHBoxLayout>
-#include <QProgressBar>
-#include <QLineEdit>
-#include <QComboBox>
-#include <QCheckBox>
-#include <QSpinBox>
-#include <QDateTimeEdit>
-#include <QSlider>
-#include <QPlainTextEdit>
-#include <QTextEdit>
-#include <QWidget>
-#include <QRadioButton>
-#include <QTableView>
-#include <QTableWidget>
-#include <QListView>
-#include <QListWidget>
-#include <QSlider>
+#include <QtWidgets/QHBoxLayout>
+#include <QtWidgets/QProgressBar>
+#include <QtWidgets/QLineEdit>
+#include <QtWidgets/QComboBox>
+#include <QtWidgets/QCheckBox>
+#include <QtWidgets/QSpinBox>
+#include <QtWidgets/QDateTimeEdit>
+#include <QtWidgets/QSlider>
+#include <QtWidgets/QPlainTextEdit>
+#include <QtWidgets/QTextEdit>
+#include <QtWidgets/QWidget>
+#include <QtWidgets/QRadioButton>
+#include <QtWidgets/QTableView>
+#include <QtWidgets/QTableWidget>
+#include <QtWidgets/QListView>
+#include <QtWidgets/QListWidget>
+#include <QtWidgets/QSlider>
 #include <QScroller>
-#include <QScrollArea>
-#include <QMenu>
-#include <QInputDialog>
-#include <QHBoxLayout>
+#include <QtWidgets/QScrollArea>
+#include <QtWidgets/QMenu>
+#include <QtWidgets/QInputDialog>
+#include <QtWidgets/QHBoxLayout>
 //#include <QGraphicsBlurEffect>
-#include <QPainter>
-#include <QColor>
+#include <QtGui/QPainter>
+#include <QtGui/QColor>
 #include <QMetaMethod>
-#include <QDebug>
+#include <QtCore/QDebug>
 
 #include <LtsSession/lts_session_data.h>