A community's moderators lock threads and ban members

Lemmy's moderation reached PrivaPub only as removals. Now a remote
community's lock and ban, relayed in its Announce, apply too:

- a lock (Announce{Lock}, or commentsEnabled false on the post) refuses
  replies to the thread, ours included, until Undo{Lock}; statuses say so
  in privapub.locked;
- a ban of a persona (Announce{Block} with the community as target, or the
  moderator's own Block sent straight to us, which is the community's ban
  and never the moderator's block of the persona) shows as blocked_by on
  the community and refuses the persona's posts and replies there until
  the Undo.

The Lemmy scenario's removal was an expected failure only because it gave
up before Lemmy's 30-second batch; it now waits, and checks the lock and
the ban live (Lemmy refuses a lock or an unban without a reason): 29
checks, none expected to fail. G-0003 and G-0006 are closed.

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

PrivaPub/Domain/Statuses/StatusService.cs

@@ -129,6 +129,9 @@ namespace PrivaPub.Domain.Statuses
 				return StatusOutcome.Fail(StatusCodes.Status404NotFound, "Record not found");
 			if (parent != default && !await VisibilityPolicy.CanSee(parent, author.Id, token))
 				return StatusOutcome.Fail(StatusCodes.Status404NotFound, "Record not found");
+			// its community's moderators locked the thread
+			if (parent is { LockedAt: not null })
+				return StatusOutcome.Fail(StatusCodes.Status422UnprocessableEntity, "Validation failed: This thread is locked");
 			// a reply in a circle stays in the circle, whichever client wrote it: Mastodon clients know nothing of groups
 			if (group == default && parent is { Visibility: PostVisibility.Circle } && !string.IsNullOrEmpty(parent.GroupId)
 				&& await _dbEntities.Groups.MatchID(parent.GroupId).ExecuteFirstAsync(token) is { DeletionAt: null } parentCircle
@@ -172,6 +175,10 @@ namespace PrivaPub.Domain.Statuses
 						break;
 					}
 				}
+			// a community that banned the persona takes nothing from it, a post or a reply
+			var community = audienceUri ?? parent?.AudienceURI;
+			if (community != default && await DB.Default.Find<BlockedBy>().Match(b => b.AvatarId == author.Id && b.ActorURI == community).ExecuteAnyAsync(token))
+				return StatusOutcome.Fail(StatusCodes.Status422UnprocessableEntity, "Validation failed: This community banned you");
 			var isLocalOnly = located;
 			var visibility = located ? PostVisibility.LocalGeo
 				: group is { IsCircle: true } ? PostVisibility.Circle