Pins across servers, both ways

An account elsewhere that pins or unpins one of its posts (Add or Remove on its `featured`) now shows those pins on its
profile here (`pinned=true`), in its order and its public posts only; a community's announce of a moderator's Add does
the same for the community. The `featured` collection itself is read with the account's counts, at most once a day, so
pins made before PrivaPub ever saw an account show too. Any other target (Smithereen's wall, a community's moderators)
is dropped. A persona's pin and unpin go to the post's audience as Add and Remove on /trophies, as Mastodon sends them.

Checked live against Mastodon (scenarios/pins.sh, 8 checks). The town's checker learnt three peer rules from the
village: Misskey and Sharkey keep a forwarded reply only with its author's LD signature (only Mastodon signs), they
count no renote by a bot, and Mastodon never sees a Lemmy vote on a post in a community. The village of 2026-10-05
checks clean, 2454 of 2454.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub/Api/Mastodon/Controllers/StatusesController.cs

@@ -405,6 +405,7 @@ namespace PrivaPub.Api.Mastodon.Controllers
 			try
 			{
 				await DB.Default.SaveAsync(new Models.Social.Pin { AvatarId = MyId, PostId = post.ID }, token);
+				await _outbox.PublishFeatured(MyId, post, featured: true, token);
 			}
 			catch (MongoDB.Driver.MongoWriteException ex) when (ex.WriteError?.Category == MongoDB.Driver.ServerErrorCategory.DuplicateKey)
 			{
@@ -415,7 +416,9 @@ namespace PrivaPub.Api.Mastodon.Controllers
 		[HttpPost("/api/v1/statuses/{id}/unpin"), Scope("write:accounts")]
 		public async Task<IActionResult> Unpin(string id, CancellationToken token)
 		{
-			await DB.Default.DeleteAsync<Models.Social.Pin>(p => p.AvatarId == MyId && p.PostId == id);
+			var unpinned = await DB.Default.DeleteAsync<Models.Social.Pin>(p => p.AvatarId == MyId && p.PostId == id);
+			if (unpinned is { IsAcknowledged: true, DeletedCount: > 0 } && await _dbEntities.Posts.MatchID(id).ExecuteFirstAsync(token) is { } post)
+				await _outbox.PublishFeatured(MyId, post, featured: false, token);
 			return await Unchanged(id, token);
 		}