Undo(Announce): now removes announce record from ActorRepository and
calls ApObjectHandler::on_announce_removed (default no-op, override
to decrement boost counts). Announce counts no longer drift.
Undo(Block): now logged at info level instead of silently ignored.
No automatic relationship restoration (spec doesn't require it).
AddActivity: now uses object["id"] as the stable ap_id (same as
CreateActivity), falling back to activity id only if object has no
id field. Fixes keying watchlist/collection items by the wrong id.
Featured collection: GET /users/{id}/featured now served by the router.
ApContentReader::get_featured_objects() has a default empty-list impl
— override to expose pinned posts without any breaking changes.
