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/history_model.cpp

@@ -40,9 +40,9 @@ bool HistoryModel::initModel(const QSqlDatabase &db, const QString &schema)
   {
     HistoryUpdate hu;
     hu.schema      = schema;
-    hu.m_id          = q.value(0).toInt();
+    hu.id          = q.value(0).toInt();
     hu.version     = q.value(1).toString();
-    hu.m_description = q.value(2).toString();
+    hu.description = q.value(2).toString();
     hu.updated     = q.value(3).toLongLong();
     hu.success     = q.value(4).toBool();
     hu.message     = q.value(5).toString();
@@ -66,13 +66,13 @@ QVariant HistoryModel::data(const QModelIndex &index, int role) const
     switch (index.column())
     {
       case Id:
-        return hu.m_id;
+        return hu.id;
       case Schema:
         return QString(hu.schema);
       case Version:
         return QString(hu.version);
       case Description:
-        return QString(hu.m_description);
+        return QString(hu.description);
       case Updated:
         return DTG::toStringMSec(hu.updated);
       case Success: