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/AudioVideoManagement/avm_export.h

@@ -0,0 +1,13 @@
+/**
+  * Stub export header for non-RTI builds
+  * When BUILD_RTI=OFF, svcAvmCommon library is not built
+  * This stub allows dependent code to compile
+  */
+#pragma once
+
+#include <QtCore/qglobal.h>
+
+// Stub export macros for non-RTI builds
+#define AVM_COMMON_EXPORT
+#define AVM_CLIENT_EXPORT
+#define AVM_SERVER_EXPORT