Migrate LTS Tools Group 6 (D&L) to Qt6

Build script changes:
- Add --group6/--no-group6 argument support to new_docker_build.sh
- Add GROUP6_TARGETS array with 11 LTS tools
- Add BUILD_GROUP6 environment variable export
- Add GROUP6 build invocation in run_build_group function

Test infrastructure:
- Create CTest test files for all 11 Group 6 tools
- Add exclusion filters in tests/CMakeLists.txt for conditional builds
- Tests follow gtest pattern: CompilationStub, Qt6ApiCompatibility, BasicFunctionality

Qt6 migration bug fixes:
- DBAdministration: Fix m_id → id member access (3 files)
- DBAdministration: Add missing QFile include in showLogFile.cpp
- DBUpdate: Add CMAKE_AUTOUIC_SEARCH_PATHS for ui/ directory
- DBUpdate: Fix m_id → id, m_description → description (3 files)

Build validation:
- DBAdministration, DBOperatorSettingsRemover, DBUpdate build successfully
- Remaining tools blocked by pre-existing Group 3 (ExerciseManagement) errors
- Policy checks passed

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

qt6-after/qt6-migrated-legatus/Lts/Tools/DBUpdate/global_updates_model.cpp

@@ -58,7 +58,7 @@ bool GlobalUpdatesModel::initModel(const QSqlDatabase &db, const QString &versio
     if (q.execAndFetch(stmt))
     {
       gu.version     = q.value(1).toString();
-      gu.m_description = q.value(2).toString();
+      gu.description = q.value(2).toString();
       gu.updated     = q.value(3).toLongLong();
     }
     int upperGuVersion = gu.version.split(QLatin1Char('.')).at(0).toInt();
@@ -104,7 +104,7 @@ QVariant GlobalUpdatesModel::data(const QModelIndex &index, int role) const
     case Version:
       return QString(gu.version);
     case Description:
-      return QString(gu.m_description);
+      return QString(gu.description);
     case Updated:
       return DTG::toStringMSec(gu.updated);
     }