In CB-442 aerozol came up with a new design for entity pages. At the same time, he added a nice looking footer, which is a little bit different to the one that we have in LB

This is a ticket to make official a common footer that we can share between projects. It should take the best of what we already have in the LB footer, and what is in the mockups of the linked ticket.

The footer should be eventually integrated into the design system. For CB, as we're still using jinja templates and not react, we can reimplement a plain html version.