Merge feature/qt6-migration-basis-modules-merge-viewer-validation into feature/migrate-lts-projects-and-application

Cherry-picks 5501d1e50 (stub-header updates, superseded by 4223ca2ff relocation); resolves 1 content + 24 modify/delete conflicts; validates BUILD_RTI=ON BUILD_GRANTLEE=ON incl. Tools Groups 6-11.

qt6-after/qt6-migrated-legatus/forward-declarations/Lts/Services/OperatorManagement/opm_dtc.h

@@ -0,0 +1,4 @@
+#pragma once
+
+// STUB-HEADER: Include generated file from build directory
+#include <Lts/Proxies/OperatorManagement/opm_dtc.h>

qt6-after/qt6-migrated-legatus/forward-declarations/Lts/Services/OperatorManagement/opm_ftc.h

@@ -0,0 +1,21 @@
+#ifndef OPM_FTC_H
+#define OPM_FTC_H
+
+// Stub header for OperatorManagement FTC functionality
+// This file is part of FilterManagement which is excluded from build
+// For non-FilterManagement builds, we provide this stub
+
+#include <QtCore/QString>
+#include <QtCore/QObject>
+
+// Forward declarations and stubs for FTC (Filter/Translation/Conversion)
+// Actual implementation is in FilterManagement plugin
+
+class OpmFtc
+{
+public:
+    virtual ~OpmFtc() = default;
+    // Stub methods - actual implementation in FilterManagement
+};
+
+#endif // OPM_FTC_H