Revert part of "mv pseudonyms and db split to separate "data separation" page"

This reverts parts of commit f9b2e260.

The technical details fit better in the secrutiy chapter because it is
supposed to give a quick overview of security measures implemented in
castellum.
1 job for revert-split-privacy in 27 seconds
Status Name Job ID Coverage
  Test
passed test #30996

00:00:27