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Cherry-picks 5501d1e50 (stub-header updates, superseded by 4223ca2ff relocation); resolves 1 content + 24 modify/delete conflicts; validates BUILD_RTI=ON BUILD_GRANTLEE=ON incl.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/Lts/Viewer/SituationMap/SymbologyImpl/symbol_dictionary_impl.cpp

@@ -824,7 +824,7 @@ int SymbolDictionaryImpl::addEtsSymbols(const QString &path)
     QStringView filePathReduced = filePath.mid(rootDir.absolutePath().size() + 1);
     // filepath 'Sonstige/Bundeswehr_Stelle.gif'
 
-    QVector<QStringView> parts = filePathReduced.split(QLatin1Char('/'));
+    QList<QStringView> parts = filePathReduced.split(QLatin1Char('/')); // Qt6: QStringView::split returns QList<QStringView>
 
     // remove filename (to get dirname's as tags:
     parts.removeLast();
@@ -2211,7 +2211,7 @@ QList<ModifierData> SymbolDictionaryImpl::symbolModifierList(const QString &base
     return QList<ModifierData>();
   }
 
-  SidcDefinitions::SymbolSet symbolSetBaseCode = SidcDefinitions::castToSymbolSet(baseSymbolCode.midRef(0, 2).toUInt());
+  SidcDefinitions::SymbolSet symbolSetBaseCode = SidcDefinitions::castToSymbolSet(baseSymbolCode.mid(0, 2).toUInt()); // Qt6: midRef removed
 
   return m_esriDictionaryProcessor->symbolModifierList(symbolSetBaseCode, modifierSector).toList();
 }