A follow request sent again carries a new id

Lemmy keeps the ids of the activities it received and never answers one again, so resending the same Follow could not
heal a follow whose Accept it lost: the village's community follow stayed pending through two resends. Each resend is
now the same follow under its own id (<follow id>-again-<n>), and an Accept naming any of them answers the follow;
the Undo still embeds the follow, so servers match it by its actor and object. Sent this way, the stuck follow was
accepted at once.

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

PrivaPub/Federation/Inbox/Handlers/AcceptHandler.cs

@@ -53,7 +53,10 @@ namespace PrivaPub.Federation.Inbox.Handlers
 		{
 			if (follow is JsonObject && Value(follow, "type") is { } type && type != "Follow")
 				return default;
-			var followId = Id(follow);
+			// (a follow sent again names the first one under a new id: FollowService.AgainId)
+			var followId = Id(follow) is { } named && named.IndexOf(Domain.Social.FollowService.Again, StringComparison.Ordinal) is var at and > 0
+				? named[..at]
+				: Id(follow);
 			var byId = followId == default
 				? default
 				: await dbEntities.Followings.Match(f => f.FollowActivityURI == followId && f.TargetActorURI == target.ActorURI).ExecuteFirstAsync(token);