Add clean-up section for personal bookmarks

[adixchen]

Beside read later tab add a clean-up tab where the user can get to do some clean up:

• delete personal (not public) bookmarks that she hasn't accessed in the last 3 years for example (public maybe if they haven't been by at least somebody else besides the user) - move the public ones to a generic account if already starred by someone
• delete personal bookmarks by tag (useful for private bookmarks) - DONE
• Danger Zone - delete account (remove account from keycloak, delete all personal bookmarks and the public bookmarks starred by someone else move to generic account