Mabni Lab native desktop application

The icon-only toolbar, alternate-label and tooltip behavior in
src/Desktop/LabToolButton.cs is a C# / WinForms adaptation of Veyon's
core/src/ToolButton.cpp and ToolButton.h.

Upstream: https://github.com/veyon/veyon
Revision: 1cebf45f6c1af8bab2c96278a58db1cf2f56685d
Copyright (c) 2006-2026 Tobias Junghans <tobydox@veyon.io>
License: GNU General Public License, version 2 or any later version.
Adaptation date: 2026-10-21. The upstream source files are retained here unchanged.

This native desktop application, including its adapted toolbar, is provided
under GPL-2.0-or-later, WITHOUT ANY WARRANTY. You may modify and redistribute
it under those terms. See COPYING for the license text.

The complete corresponding native desktop source and build instructions are
included in Source/MabniLab.Desktop.Source.zip beside the installed Windows
application. The teacher and student services are separate processes; their
behavior was not replaced with Veyon in this UI update. No Veyon branding,
identity keys or installed configuration were imported.
