M6: provenance fixes, stored features, community edits that are real edits

- A fetched ObjectRecord no longer wears the signature, key, signed headers and @context
  of the activity that caused the fetch, and its ReceivedAt is the fetch's own time. Its
  activity fields now name the trigger. Provenance answers signature null and
  fetchedBy "instance-actor". Migration _008 clears the old fetched records.
- ObjectRecords store their ObjectFeatures extensions and context namespaces (migration
  _009 fills older records in batches), so statistics can count them. Provenance reads the
  stored lists.
- ForeignAvatar.Features records what an actor document uses (ActorFeatures): featured,
  shared inbox, FEP-521a, FEP-8b32, identity proofs, Misskey fields, indexable,
  undiscoverable, locked, key size, and more.
- RemoteEdits.Apply and RemoteDeletes.Remove are shared by the Update, Delete and Announce
  handlers. A community-wrapped Update is now an edit only when newer, refreshes polls
  and media otherwise, revises the ObjectRecord and re-resolves quotes. A
  community-wrapped Delete now tombstones the object, removes its ObjectRecord, reblogs
  and timeline rows, and lowers the reply count. Any deleted quoting post lowers the
  quoted post's quote count.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ELjqpznMFMNrJoJUj6K5p2

PrivaPub/Federation/Inbox/Handlers/UpdateHandler.cs

@@ -18,7 +18,6 @@ namespace PrivaPub.Federation.Inbox.Handlers
 {
 	public class UpdateHandler : IActivityHandler
 	{
-		const int MaxRevisions = 20;
 
 		readonly DbEntities _dbEntities;
 		readonly ILocalActorService _localActors;
@@ -70,69 +69,10 @@ namespace PrivaPub.Federation.Inbox.Handlers
 			}
 			Arrival.About(note.Type, post.Visibility, post.CreationDate);
 
-			post.Poll = note.Poll ?? post.Poll;
-			post.QuotePolicy = note.QuotePolicy;
-			post.Video = note.Video ?? post.Video;
-			post.Audio = note.Audio ?? post.Audio;
-			post.Event = note.Event ?? post.Event;
-			if (!IsEdit(note, post))
-			{
-				Arrival.Accept("refresh");
-				await DB.Default.SaveAsync(post, token);
-				await _records.Revise(note, Id(activity), token);
-				await Requote(post, note, token);
-				return;
-			}
-
-			Arrival.Accept("edit");
-			post.Revisions.Add(new PostRevision
-			{
-				Title = post.Title,
-				SpoilerText = post.SpoilerText,
-				ContentHtml = post.ContentHtml,
-				HasContentWarning = post.HasContentWarning,
-				EditedAt = post.EditedAt ?? post.CreationDate
-			});
-			if (post.Revisions.Count > MaxRevisions)
-				post.Revisions.RemoveRange(0, post.Revisions.Count - MaxRevisions);
-
-			var mentions = new List<PostMention>();
-			foreach (var mention in note.Mentions)
-			{
-				var local = await _localActors.FindByUri(mention.ActorURI, token);
-				mentions.Add(new PostMention { ActorURI = mention.ActorURI, Handle = mention.Handle, IsLocal = local != default, AccountId = local?.Id });
-			}
-
-			post.Title = note.Title;
-			post.SpoilerText = note.SpoilerText;
-			post.Excerpt = note.Excerpt;
-			post.Source = note.Source;
-			post.Emojis = note.Emojis.ToList();
-			post.CoverURL = note.CoverURL;
-			post.Link = note.Link;
-			post.HasContentWarning = note.Sensitive;
-			post.Text = note.ContentHtml;
-			post.ContentHtml = note.ContentHtml;
-			post.Language = note.Language;
-			post.Tags = note.Tags.ToList();
-			post.Mentions = mentions;
-			post.Media = note.Attachments.ToList();
-			post.EditedAt = note.Updated ?? DateTime.UtcNow;
-			post.UpdateDate = DateTime.UtcNow;
-			await DB.Default.SaveAsync(post, token);
-			await _records.Revise(note, Id(activity), token);
-			await Requote(post, note, token);
-			if (!string.IsNullOrEmpty(post.GroupId) && await _localActors.FindById(Models.Federation.LocalActorKind.Group, post.GroupId, token) is { IsCircle: false } community)
+			var edited = await RemoteEdits.Apply(post, note, Id(activity), _localActors, _records, _quotes, token);
+			Arrival.Accept(edited ? "edit" : "refresh");
+			if (edited && !string.IsNullOrEmpty(post.GroupId) && await _localActors.FindById(Models.Federation.LocalActorKind.Group, post.GroupId, token) is { IsCircle: false } community)
 				await _groups.Announce(community, activity.AsObject(), post.ObjectURI, isNewPost: false, token);
 		}
-
-		static bool IsEdit(NoteDocument note, PostEntity post) =>
-			note.Updated is { } updated && updated > (post.EditedAt ?? post.CreationDate);
-
-		async Task Requote(PostEntity post, NoteDocument note, CancellationToken token)
-		{
-			if (note.QuoteUri != post.QuoteURI || note.QuoteAuthorization != post.QuoteAuthorizationURI || post.QuoteState != QuoteState.Accepted)
-				await _quotes.Resolve(post, note, token);
-		}
 	}
 }