R7 custom emoji: the server's own, added by administrators, sent on posts, profiles and reactions

LocalEmoji, a new collection (unique shortcode whatever its case, never renamed: the shortcode is its id elsewhere),
managed on /clientapi/admin/emoji/list|insert|update|delete and kept in the staff's log (emoji.insert, .update,
.delete). Its picture goes through IMediaService.EmojiImage: PNG, GIF, WebP or JPEG up to 256 KB, a PNG within 256 px
with alpha kept (an animated GIF or WebP stays an animated GIF, with a still PNG), keep=none, shrunk until it fits
GoToSocial's 100 KiB, held by ServerUse "emoji:<shortcode>" so the janitor and the audit leave it. LocalEmojis keeps the
offered ones in memory, reloaded on every change: GET /api/v1/custom_emojis is real; local posts (words, title, warning,
poll options, each revision) and profiles keep the emoji they name; Notes, Questions, actors and EmojiReacts carry
Mastodon's Emoji tag with its id, served as an Emoji at /emojis/{shortcode} (410 once deleted; the path awaits the
owner's confirmation); a persona reacts with one (Pleroma's reactions, announcements). A restore keeps the live emoji
as it keeps the settings, and trashes server pictures nothing holds. tools/pasture/scenarios/emoji.sh joins batch A.

Verified: built, and run locally against a scratch database (uploads of every type, animation kept, metadata gone,
refusals, rendering, reactions, history, announcements, delete and revive, backup and restore, media audit). The
pasture scenario and the sweep were not run.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WpVCoDeM1qUTRp4fXQdfof

PrivaPub/Domain/Media/MediaAudit.cs

@@ -10,7 +10,7 @@ namespace PrivaPub.Domain.Media
 	// What the media directory holds against what the database says holds it, and, with fix, the two made to agree:
 	// - a persona's current avatar or header with no row (they had none before) becomes a row of its own;
 	// - media of a deleted post or of a deleted persona go to the trash, and a picture of the server's own (ServerUse) that
-	//   its settings no longer name;
+	//   its settings no longer name (its thumbnail) or no custom emoji holds;
 	// - rows whose files are gone go to the trash;
 	// - files nothing holds (deleted posts' media and replaced pictures, from before media were trashed) get a trashed row
 	//   each.
@@ -60,9 +60,12 @@ namespace PrivaPub.Domain.Media
 			var ownerIds = rows.Select(r => r.OwnerAvatarId).Where(id => id != null).Distinct().ToList();
 			var liveOwners = (await DB.Default.Find<Avatar>().Match(a => ownerIds.Contains(a.ID) && !a.DeletionAt.HasValue).Project(a => a.Include(x => x.ID)).ExecuteAsync(token))
 				.Select(a => a.ID).ToHashSet();
-			// (the server's own pictures belong to nobody: they are held while the settings name them)
+			// (the server's own pictures belong to nobody: they are held while the settings name them, or a custom emoji that is
+			// not deleted, disabled ones too)
 			var settings = await DB.Default.Find<Models.ServerSettings>().Match(x => x.ID == Models.ServerSettings.Name).ExecuteFirstAsync(token);
 			var serverHeld = new HashSet<string> { settings?.ThumbnailMediaId };
+			serverHeld.UnionWith((await DB.Default.Find<Models.Post.LocalEmoji>().Match(e => e.DeletedAt == null).Project(e => e.Include(x => x.MediaId))
+				.ExecuteAsync(token)).Select(e => e.MediaId).Where(id => id != null));
 			var ofDeleted = rows.Where(r => r.ServerUse != null ? !serverHeld.Contains(r.ID)
 				: (r.PostId != null && !livePosts.Contains(r.PostId)) || (r.OwnerAvatarId != null && !liveOwners.Contains(r.OwnerAvatarId))).ToList();
 			var missing = rows.Except(ofDeleted).Where(r => !string.IsNullOrEmpty(r.FilePath) && !files.Contains(r.FilePath)).ToList();