science/kalzium: Decruft and prep for Qt 6.11.x

Modernize deps for Qt6/KF6 and remove obsolete patch. Qt6 and this
project require the C++17 standard.

New patch added to remove unused KF6 Archive component and to account
for the Avogadro:Gui target requiring the Qt::Concurrent target.

Pet portclippy(1).

MFH: 2026Q2