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/EffectShowClient/esc_dtc.h

@@ -0,0 +1,13 @@
+#pragma once
+
+// STUB-HEADER: Diese Datei wird normalerweise von ddsdtc generiert
+// Für die Migration erstellen wir minimale Forward-Declarations
+
+namespace EffectShowClient
+{
+namespace Interface
+{
+class Dtc;
+class Ftc;
+} // namespace Interface
+} // namespace EffectShowClient