Seven call sites stop reaching through the embedded *s3.Client and
instead use the high-level storage.Store methods. Same runtime behavior
on the AWS path; opens the door to the Filesystem backend for
self-hosters.
avatar.go retains an S3-specific path for public-ACL + cache-control
on uploaded avatars and falls back to ServiceUnavailable on non-S3
backends. A future PublicStore interface could clean that up.
unibox/storage.go GetBody now propagates the emsg.DecodeBinary error
that the original code dropped on the floor.
Matthew Meszaros
59b515cad4