P6: quote posts, received and sent (FEP-044f and the older keys)

- Received quotes: read from `quote`, `quoteUrl`, `quoteUri`, `_misskey_quote` or a FEP-e232 Link tag; the quoted post
  is fetched once; a quoteAuthorization stamp is verified field by field on the quoted author's origin; a consent
  quote without a stamp is pending; an older-key quote of a public post is shown; Delete of a stamp revokes. Counts
  and a `quote` notification follow the accepted state. The `quote-inline` fallback survives sanitising and is removed
  from content when the real quote is shown.
- Personas quote through `quoted_status_id`: posts that state a quote policy get a QuoteRequest and stay pending until
  an Accept brings a stamp we can verify, then an Update adds quoteAuthorization; posts that state none are quoted
  the older way, without `quote`; another persona's posts cannot be quoted yet (we issue no stamps). Quoting posts
  are delivered to the quoted author too.
- Mastodon API: Status.quote (with the quoted status one level deep), quotes_count, quote_approval from the remote
  policy, GET /api/v1/statuses/:id/quotes, `quote` notifications, and api_versions.mastodon = 7.

Checked live: GoToSocial's author-only quote policy is respected.

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

PrivaPub/Domain/Statuses/PollService.cs

@@ -233,30 +233,11 @@ namespace PrivaPub.Domain.Statuses
 				return JobOutcome.Done;
 			await Closing(post, author, token);
 			if (!post.IsLocalOnly)
-				await _outbox.Publish(author, post, Update(post, author), token);
+				await _outbox.Publish(author, post, ActivityPubRenderer.UpdateOf(post, author, $"poll-{DateTime.UtcNow.Ticks}"), token);
 			return JobOutcome.Done;
 		}
 
 		protected virtual Task Closing(PostEntity post, LocalActor author, CancellationToken token) => Task.CompletedTask;
-
-		static JsonObject Update(PostEntity post, LocalActor author)
-		{
-			var question = post.Visibility == PostVisibility.Direct
-				? ActivityPubRenderer.DirectNote(post, author, Array.Empty<(string, string)>(), post.ContextURI)
-				: ActivityPubRenderer.Note(post, author, default, post.InReplyToURI);
-			question["to"] = new JsonArray(post.To.Select(t => (JsonNode)t).ToArray());
-			question["cc"] = new JsonArray(post.Cc.Select(c => (JsonNode)c).ToArray());
-			return new JsonObject
-			{
-				["@context"] = ActivityPubRenderer.Context(),
-				["id"] = author.ActivityUri($"update-{post.ID}-poll-{DateTime.UtcNow.Ticks}"),
-				["type"] = "Update",
-				["actor"] = author.Uri,
-				["to"] = question["to"]!.DeepClone(),
-				["cc"] = question["cc"]!.DeepClone(),
-				["object"] = question
-			};
-		}
 	}
 
 	public class PollCloseJob : PollRefreshJob