Decide access request items

Computed evaluation of whether the caller can fulfill a request.

Display info for the filer's human owner (labelling only, not authorization).

Server-resolved from filer_owner_id (falling back to created_by when the former is null, mirroring what consumers render) so they don't need users:read (or a roster fetch) just to label a row. Absent when the id doesn't resolve to a user (service-account filers, purged rows) or on mutation responses, which skip the enrichment.