#1 count_accepted_followers / get_accepted_followers_page: new DB-side
methods on FollowRepository — no more loading all followers into memory
to count or page them.
#2 Move re-follows are now non-blocking: tokio::spawn instead of
awaiting each sign_and_send inside receive() — inbox handler no longer
stalls for slow remote servers during account migration.
#3 Remove get_local_objects_for_user from ApContentReader (dead code).
Backfill and outbox both use the paginated get_local_objects_page.
#6 Rename backfill_outbox → import_remote_outbox with a clear doc
explaining the direction (import FROM a remote server, not to a follower).
#7 also_known_as: Option<String> → Vec<String> on ApUser, LookedUpActor,
and DbActor. from_json now stores all aliases; move_act.rs checks all.
Mentions: broadcast_create_note / broadcast_update_note now accept
mentioned_inboxes: Vec<Url> — delivery goes to followers + mentioned
actors who aren't already followers. Deduplication is done before
sending. Pass vec![] if note has no external mentions.
Docs: ApObjectHandler and ApContentReader now have complete doc comments
with contracts, idempotency guidance, and error-handling semantics.
