Complete Qt6 migration: full clean build green across groups G1-G12 incl. runtime plugin set

new_docker_build.sh gains Group 12 (212 GUI/Data plugins); fixes LtsUtilsGuiDds visibility (LTO-stripped exports), LtsProjectionWorkstation unity name shadow, 6 unity-off dirs (dup file-scope statics, ddsftc INTERFACE sources) and reconfigures BUILD_FILTERMANAGEMENT/BUILD_PLUGINS_SERVICEMONITOR=ON

qt6-after/qt6-migrated-legatus/Lts/Plugins/PlanOverlays/Gui/flm_reply_handler.cpp

@@ -25,7 +25,7 @@ namespace PlanOverlaysPlugin
 
   void FileManagementReplyHandler::onGetFileContentDataReply( const FileManagement::GetFileContentDataReply & replyObject )
   {
-    m_content = replyObject.content();
+    m_content = replyObject.content;
     m_requestHelper->requestReply(replyObject);
   }