Session 025: Fix QTextCodec migration issues

- Z/src/qsql_informix/qsql_informix.cpp: Fixed QTextCodec include path
  (QtCore → QtGui) as QTextCodec moved to QtGui module in Qt6
- Z/src/qsql_informix/CMakeLists.txt: Added Qt6::Gui dependency required
  for QTextCodec
- Lts/Tools/TextEditorTest/textedit.cpp: Fixed Qt::codecForHtml →
  QTextCodec::codecForHtml (static method on QTextCodec class in Qt6)

These are minimal fixes required for Qt6 compatibility. QTextCodec is now
part of QtGui module and codecForHtml is a static method on QTextCodec
class rather than Qt namespace function.

Co-authored-by: Copilot <2235566219+Copilot@users.noreply.github.com>

qt6-after/qt6-migrated-legatus/Lts/Tools/TextEditorTest/textedit.cpp

@@ -367,7 +367,7 @@ bool TextEdit::load(const QString &f)
     return false;
 
   QByteArray data = file.readAll();
-  QTextCodec *codec = Qt::codecForHtml(data);
+  QTextCodec *codec = QTextCodec::codecForHtml(data);
   QString str = codec->toUnicode(data);
   if (Qt::mightBeRichText(str)) {
     QUrl baseUrl = (f.front() == QLatin1Char(':') ? QUrl(f) : QUrl::fromLocalFile(f)).adjusted(QUrl::RemoveFilename);

qt6-after/qt6-migrated-legatus/Z/src/qsql_informix/CMakeLists.txt

@@ -29,6 +29,7 @@ SET(ifx_SRCS
 ADD_LIBRARY(qsql_informix SHARED ${ifx_SRCS})
 TARGET_LINK_LIBRARIES(qsql_informix
   Qt6::Core
+  Qt6::Gui
   Qt6::Sql
   Qt6::Core5Compat
   ${ICLIENT_SDK_LIBRARIES}

qt6-after/qt6-migrated-legatus/Z/src/qsql_informix/qsql_informix.cpp

@@ -21,7 +21,7 @@
 #include <QtSql/QSqlRecord>
 #include <QtSql/QSqlQuery>
 #include <QtCore/QStringList>
-#include <QtCore/QTextCodec>
+#include <QtGui/QTextCodec>
 #include <QtCore/QTimer>
 #include <QtCore/QVariant>
 #include <QtCore/QMetaType>