Improve the readability of the data protection agreement during registration

Description

Currently, the readability of the privacy agreement is very limited because the window is very small on a desktop and mobile view. A link to the text is missing.

Goal

Insert a link to the privacy agreement. Either remove the privacy agreement window or make it larger or better readable on mobile devices. That should still be discussed.

Links / references

https://gitlab.com/foodsharing-dev/foodsharing-it-support/issues/253!