Blocks, mutes, bookmarks, pins and reports

- Blocks are per persona and never federate (a Block activity would tell
  the other server who blocked whom): the blocked account is removed as a
  follower, with a Reject{Follow} if it is remote, unfollowed, cleared from
  home and notifications, and refused with Reject if it follows again.
- Mutes (optionally timed, optionally sparing notifications) and per-
  persona domain blocks keep authors out of home timelines, notifications
  and every status list the API returns; the boosts of a hidden author's
  posts are hidden too.
- Bookmarks and pins (at most five, public or unlisted, own posts) with
  their Mastodon endpoints and flags; pinned posts are the actor's
  `featured` collection at /trophies, and `featuredTags` points at
  /tattoos.
- Reports: /api/v1/reports stores the report and, when forwarding to a
  remote account, sends Flag from the instance actor, so the reporting
  persona is never named to the other server. An inbound Flag about a local
  persona or its posts becomes a report; moderators list and resolve them
  under /clientapi/moderator/reports.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub/Domain/Timelines/Fanout.cs

@@ -53,6 +53,7 @@ namespace PrivaPub.Domain.Timelines
 					break;
 			}
 
+			recipients.ExceptWith(await Relationships.Hidden.RecipientsHiding(recipients, post.ActorURI, token));
 			foreach (var avatarId in recipients)
 			{
 				try