Merge feature/qt6-migration-basis-modules-services into feature/qt6-migration-basis-modules

Resolves 17 conflicts against legacy Qt5 semantics; validates with BUILD_RTI=ON BUILD_GRANTLEE=ON.

qt6-after/qt6-migrated-legatus/.forward-declarations/include/ProjectDataManagement/pdm_enums.hpp

@@ -0,0 +1,7 @@
+// Stub file for pdm_enums.hpp - used when BUILD_RTI=OFF
+#ifndef PDM_ENUMS_HPP
+#define PDM_ENUMS_HPP
+
+// Minimal stub - actual enums generated by rtiddsgen when BUILD_RTI=ON
+
+#endif // PDM_ENUMS_HPP