Add a Toolbars settings page: icon size, text with icons, lock

A new page in Configurer QElectroTech, "Barres d'outils", sets for
every window (folio editor, element editor, title block editor):
- the icon size: default, 16, 24, 32 or 48 px
- the buttons: icon only, text beside the icon, or text under it
- locking the toolbars so they can't be dragged out of place

OK applies it to the open windows at once. The defaults are Qt's
own, and a default value removes its key, so nothing changes for
anyone who never opens the page. A toolbar inside a panel is left
alone; only the window's own toolbars are locked.

New test tst_toolbarsettings: defaults change nothing, saved values
reach every toolbar of an open window, back to defaults removes the
keys.

Third stage of discussion #1319.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

sources/qetapp.cpp

@@ -42,6 +42,7 @@
 #include "ui/configpage/generalconfigurationpage.h"
 #include "ui/configpage/shortcutsconfigpage.h"
 #include "ui/configpage/shortcutbarconfigpage.h"
+#include "ui/configpage/toolbarsconfigpage.h"
 #include "machine_info.h"
 #include "TerminalStrip/ui/terminalstripeditorwindow.h"
 #include "qetversion.h"
@@ -2225,6 +2226,7 @@ void QETApp::configureQET()
 	cd.addPage(new PrintConfigPage());
 	cd.addPage(new ShortcutsConfigPage());
 	cd.addPage(new ShortcutBarConfigPage());
+	cd.addPage(new ToolbarsConfigPage());
 #ifdef QET_SPACEMOUSE_SUPPORT
 	cd.addPage(new SpaceMouseConfigPage());
 #endif