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/VideoOverlayManagement/dds_handler.cpp

@@ -8,6 +8,7 @@
 
 #include "dds_handler.h"
 
+#if BUILD_RTI
 #include <DDS/Core/pacemaker.h>
 
 namespace VideoOverlayManagement
@@ -42,3 +43,4 @@ bool DdsHandler::init(const QStringList &qosFileList)
 
 
 } // Namespace VideoOverlayManagement
+#endif // BUILD_RTI