Followed hashtags, and a tag's week of use

tags/:name shows the tag's last seven days in public posts PrivaPub holds
(uses and authors, as Mastodon gives them) and whether the persona follows
it; follow, unfollow and followed_tags replace the stubs. A public post that
is neither a boost nor a reply comes, as it arrives, to the homes of those
following one of its tags. Nothing is fetched for a followed tag and no
other server hears of it. Posts are indexed by tag.

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

PrivaPub/Domain/Timelines/Fanout.cs

@@ -43,6 +43,14 @@ namespace PrivaPub.Domain.Timelines
 					if (!string.IsNullOrEmpty(post.AudienceURI))
 						foreach (var member in await _dbEntities.Followings.Match(f => f.TargetActorURI == post.AudienceURI && f.State == FollowState.Accepted).ExecuteAsync(token))
 							recipients.Add(member.AvatarId);
+					// a public post (not a boost, not a reply) comes to those following one of its hashtags, as on Mastodon
+					if (post.Visibility == PostVisibility.Public && post.Tags.Count > 0 && string.IsNullOrEmpty(post.ReblogOfPostId)
+						&& string.IsNullOrEmpty(post.InReplyToURI) && string.IsNullOrEmpty(post.AnsweringToPostId))
+					{
+						var tags = post.Tags.ToList();
+						foreach (var followed in await DB.Default.Find<FollowedTag>().Match(t => tags.Contains(t.Name)).ExecuteAsync(token))
+							recipients.Add(followed.AvatarId);
+					}
 					break;
 				case PostVisibility.Direct when !string.IsNullOrEmpty(post.ConversationId):
 					var conversation = await _dbEntities.DmGroups.MatchID(post.ConversationId).ExecuteFirstAsync(token);