Qt6 Migration: BUILD_RTI guards und CMake fixes

- BUILD_RTI conditional compilation für RTI Connext DDS dependencies
- Namespace fixes in core_dtc.h (Core:: → DDS::Core::)
- CMakeLists.txt: BUILD_RTI option und conditional dependencies
- Handler minelayer: namespace closing mit BUILD_RTI guard
- Build erfolgreich mit BUILD_RTI=OFF validiert

Signed-off-by: Torsten Wierschin <torsten.wierschin@life-maps.com>

qt6-after/qt6-migrated-legatus/Lts/Services/RoutingServiceNG/session_handler.cpp

@@ -12,6 +12,7 @@
 #include <DDS/Generic/topic_type_plugin.h>
 #include <QVector>
 
+#if BUILD_RTI
 namespace RoutingService
 {
 
@@ -137,3 +138,4 @@ std::vector<TopicDispatcherInterface *> SessionHandler::topicsToRouteToSv() cons
 }
 
 } // namespace RoutingService
+#endif // BUILD_RTI