Posts reach their audience, edits follow them, deletes leave a tombstone

OutboxPublisher works out who a post goes to, Mastodon's way: followers'
shared inboxes for public, unlisted and followers-only; every mentioned
remote account's own inbox; the recipients only for direct; the parent's
author for a reply; a community's followers for a post in it; nobody for
a circle. Creates, updates and deletes all use it.

- Local posts take a visibility (public, unlisted, followers-only) and a
  spoiler text next to the content-warning flag.
- /clientapi/post/update keeps the previous version as a revision,
  re-renders, and sends Update{Note} with `updated` to the same to/cc.
- Deleting is now soft: the content, title, spoiler, media and revisions
  are cleared, timeline entries removed, the parent's reply count goes
  down, Delete goes to the stored audience, and the object answers 410
  with a Tombstone instead of 404.
- Editing a persona's profile sends Update{Person} to its followers.

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

PrivaPub/Middleware/SocialPubConfigurations.cs

@@ -57,6 +57,7 @@ namespace PrivaPub.Middleware
 				.AddSingleton<ILocalActorService, LocalActorService>()
 				.AddSingleton<IRemoteActorService, RemoteActorService>()
 				.AddSingleton<IDeliveryService, DeliveryService>()
+				.AddSingleton<IOutboxPublisher, OutboxPublisher>()
 				.AddSingleton<IInboxReceiver, InboxReceiver>()
 				.AddSingleton<IActivityHandler, FollowHandler>()
 				.AddSingleton<IActivityHandler, AcceptHandler>()