Allow dark theming color for default background

[Lumrenion]

My nextcloud installation has a rather light background image. When I select "Default images" in the dashboard, the greeting text as well as header icons turn white and are not readable. Same goes for "plain color".

I cannot find any way to set the color of header icons in configuration. This should be added

[raimund-schluessler]

This is nothing we can solve here and needs to be handled in the server repository, see nextcloud/server#25952. This repository here is only for the components shown inside the widgets, not the whole dashboard itself.