Domain blocks: suspend, silence, reject media

DomainBlock (domain, severity, reject-media, public and private comment)
covers the domain and its subdomains. Admins manage them under
/clientapi/admin/domainblocks/{list,insert,delete}; the set is kept in
memory, reloaded on every change and at most five minutes stale.

A suspended domain is refused by FederationHttp.IsAllowed, so nothing is
fetched from it and no job delivers to it, and the inbox drops its
activities with a 202 before fetching any key. Reject-media strips the
attachments of posts from that domain. Silence is recorded for the
timelines and notifications that arrive in P1.2.

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

PrivaPub/Federation/Inbox/InboxReceiver.cs

@@ -1,4 +1,5 @@
 using PrivaPub.Federation.Actors;
+using PrivaPub.Federation.Moderation;
 using PrivaPub.Federation.Objects;
 using PrivaPub.Federation.Signing;
 using PrivaPub.Infrastructure.Jobs;
@@ -28,13 +29,16 @@ namespace PrivaPub.Federation.Inbox
 		readonly ILocalActorService _localActors;
 		readonly IRemoteActorService _remoteActors;
 		readonly IJobQueue _queue;
+		readonly IDomainBlocks _domainBlocks;
 		readonly ILogger<InboxReceiver> _logger;
 
-		public InboxReceiver(ILocalActorService localActors, IRemoteActorService remoteActors, IJobQueue queue, ILogger<InboxReceiver> logger)
+		public InboxReceiver(ILocalActorService localActors, IRemoteActorService remoteActors, IJobQueue queue, IDomainBlocks domainBlocks,
+			ILogger<InboxReceiver> logger)
 		{
 			_localActors = localActors;
 			_remoteActors = remoteActors;
 			_queue = queue;
+			_domainBlocks = domainBlocks;
 			_logger = logger;
 		}
 
@@ -69,6 +73,8 @@ namespace PrivaPub.Federation.Inbox
 			var parameters = HttpSignatures.Parse(request.Headers["Signature"].ToString());
 			if (parameters == default)
 				return new(StatusCodes.Status401Unauthorized, "missing or unreadable Signature header");
+			if (_domainBlocks.IsSuspended(HostOf(parameters.KeyId)) || _domainBlocks.IsSuspended(HostOf(actorUri)))
+				return new(StatusCodes.Status202Accepted);
 
 			var requestProblem = HttpSignatures.CheckRequest(request, parameters, body);
 			if (requestProblem != default)
@@ -99,6 +105,8 @@ namespace PrivaPub.Federation.Inbox
 			return new(StatusCodes.Status202Accepted);
 		}
 
+		static string HostOf(string uri) => Uri.TryCreate(uri, UriKind.Absolute, out var parsed) ? parsed.Host : default;
+
 		async Task<InboxResult> ShapeProblem(string type, JsonNode activity, string actorUri, CancellationToken token)
 		{
 			var activityId = Id(activity);