Feature: "Interact via the fediverse" next to the Share button
A visitor can now reply/like/boost a post from their own fediverse
server straight from the top of the post, next to Share. Reuses the
existing fedi-remote flow (click -> asks for your server -> redirects to
your instance's authorize_interaction for this post's URI). Hidden for
the owner/admin (their own post) and when AP is off. Removed the
now-duplicate CTA that sat lower in the fediverse section, so there is
one prominent place. Dropped the now-unused _postAbsUrl var.
Browser-verified: present in the share row for visitors, absent for the
owner, and the click pops the server-input form targeting the post URI.
Co-Authored-By: Claude Opus 4.8 <noreply@…>