Enable/disable automatic board deletion

[SelinaBuff]

Discussed in #3004

^{Originally posted by SelinaBuff May 24, 2023}
Delete board after (6 weeks) Function in menu (activate/deactivate).

I think it would be appropriate if we could incorporate this into the new template page. It's best to do it right at the beginning when opening a new board. This can be activated or deactivated at any time in the general settings.

[brandstetterm]

Some of the functionality has already been implemented in #4048