P7: downvotes go out, and feeds are read through the server's reader

Votes out. A persona's downvote is a Dislike (POST /api/v1/statuses/:id/downvote and /undownvote, the viewer's own as
privapub.votes.downvoted). One vote a post: a changed vote is sent as the new vote alone, as Lemmy sends one, since an
Undo of the old one beside it could arrive after it and take the new one away; Undo goes only when a vote is taken back.
A vote on a post in a remote community goes to the community, which counts it, and to the author only when on another
server: one copy a server, since PieFed drops a second copy of an activity it has just seen. Mbin keeps a favourite
apart from a vote, so there a favourite stays after a switch to a downvote.

Feeds followed (owner decision 2026-10-07: through the server). Following a feed (Lemmy's multi-community, PieFed's feed)
keeps a FeedSubscription for the persona and nothing else; the new Service privapub_feeds (LocalActorKind.Reader,
reserved by migration _017) follows every community of the feeds read here, reconciled when a persona follows or leaves
one, when a feed's list is read again (kept as it was when it cannot be read) and every six hours. Its Following rows
carry FollowerKind, so nobody's home gets what it brings in and its unanswered follows are sent again as its own. The
persona reads GET /api/v1/timelines/feed/:id (the feed's threads, ours included) and lists its feeds at GET /api/v1/feeds.

Checked in the pasture, every scenario: 873 pass. The 14 failures are Hubzilla's (identical on the previous commit:
Hubzilla no longer answers a follow in this pasture since its restore) and two activities Smithereen never sent;
followsync passes once the pasture's restore is older than the 14-day pause. Live: alice's downvotes count as downvotes
on Lemmy 1.0 and PieFed, replacing her upvote; Lemmy 1.0 and PieFed take privapub_feeds' follows and their threads reach
the feed timelines.

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

PrivaPub/Infrastructure/Data/Indexes.cs

@@ -26,6 +26,7 @@ namespace PrivaPub.Infrastructure.Data
 			await Plain<Post>(token, p => p.WallURI, p => p.ID);//a persona's wall (FEP-400e)
 			await Plain<Post>(token, p => p.ConversationId, p => p.ID);
 			await Plain<Post>(token, p => p.InReplyToURI);
+			await Plain<Post>(token, p => p.AudienceURI, p => p.ID);//a feed's timeline: the posts of its communities
 			// who boosted what: a persona's boosts of the posts a page shows were a scan of every post under load
 			// (tools/pasture/load.sh), and a post's boosts and replies are read for its counts and context
 			await Plain<Post>(token, p => p.AuthorAccountId, p => p.ReblogOfPostId);
@@ -167,6 +168,9 @@ namespace PrivaPub.Infrastructure.Data
 			await Plain<ObjectRecord>(token, r => r.PostId);
 			await Unique<DeletedObject>(d => d.ObjectURI, Builders<DeletedObject>.Filter.Gt(d => d.ObjectURI, ""), token);
 			await DB.Default.Index<DeletedObject>().Key(d => d.DeletedAt, KeyType.Ascending).Option(o => o.ExpireAfter = TombstoneLifetime).CreateAsync(token);
+			await DB.Default.Index<FeedSubscription>().Key(s => s.AvatarId, KeyType.Ascending).Key(s => s.FeedActorURI, KeyType.Ascending)
+				.Option(o => o.Unique = true).CreateAsync(token);
+			await Plain<FeedSubscription>(token, s => s.FeedActorURI);
 			await Unique<ThreadCollection>(c => c.URI, Builders<ThreadCollection>.Filter.Gt(c => c.URI, ""), token);
 			await DB.Default.Index<ThreadCollection>().Key(c => c.ReadAt, KeyType.Ascending).Option(o => o.ExpireAfter = ThreadCollectionLifetime).CreateAsync(token);
 			await DB.Default.Index<Downvote>().Key(d => d.PostId, KeyType.Ascending).Key(d => d.ActorURI, KeyType.Ascending).Option(o => o.Unique = true).CreateAsync(token);

PrivaPub/Infrastructure/Data/Migrations/_017_the_reader_has_its_name.cs

@@ -0,0 +1,24 @@
+using MongoDB.Entities;
+
+using PrivaPub.Federation.Actors;
+using PrivaPub.Models.Federation;
+using PrivaPub.Models.User;
+
+namespace PrivaPub.Infrastructure.Data.Migrations
+{
+	// the feeds reader's name (LocalActorService.ReaderUserName) is the server's, as the reporter's is: a persona or group
+	// already holding it would be hidden behind the reader, so the upgrade stops and says so
+	public class _017_the_reader_has_its_name : IMigration
+	{
+		public async Task UpgradeAsync()
+		{
+			var held = await DB.Default.Find<ReservedName>().Match(r => r.Name == LocalActorService.ReaderUserName).ExecuteFirstAsync();
+			if (held is { OwnerKind: LocalActorKind.Reader })
+				return;
+			if (held != default)
+				throw new InvalidOperationException(
+					$"The name {LocalActorService.ReaderUserName} belongs to a {held.OwnerKind} ({held.OwnerId}); rename it before upgrading");
+			await DB.Default.SaveAsync(new ReservedName { Name = LocalActorService.ReaderUserName, OwnerKind = LocalActorKind.Reader });
+		}
+	}
+}