Adds Mastodon-style `rel=me` link verification, and creates a background job to verify said links
Closes#9341

Co-authored-by: ThatOneCalculator <kainoa@t1c.dev>
Co-authored-by: Namekuji <nmkj@waah.day>
Reviewed-on: https://codeberg.org/calckey/calckey/pulls/10506