A file lives exactly as long as something holds it

Deleting a post, editing media out, replacing an avatar or a header, and removing a whole root deleted no file: every
one stayed on disk and publicly served from /media/files with a year-long immutable cache, its row orphaned. Now every
upload is a row, profile pictures too (Kind avatar or header, ProfileOfAvatarId), and each of those acts trashes what
it held, as does an upload never posted for a day and a dropped scheduled post. A trashed row is marked in one
conditional update (an upload attached meanwhile is left alone), its files move into media-trash, beside the media
root and outside what /media/files serves, and the janitor deletes them a day later. Nothing is deleted for looking
unused.

Along the way: a profile picture that isn't an image, or can't be read, answers 422 instead of being silently ignored
with a 200; a removed root's scheduled posts are dropped, so nothing of it publishes later; media rows get indexes
(they had none), and the janitor's first pass comes five minutes after boot instead of an hour.

`PrivaPub admin media audit [--fix]` compares the disk with the database. With --fix (as www-data) it gives the
pictures personas show today a row, and trashes media of deleted posts or personas, rows whose files are missing, and
files nothing holds: the leftovers of every deletion until now. MediaLifecycleTests covers each act, that the trash is
never served, and the audit.

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

PrivaPub/Api/Mastodon/Controllers/StatusesController.cs

@@ -111,7 +111,8 @@ namespace PrivaPub.Api.Mastodon.Controllers
 				return Error(StatusCodes.Status422UnprocessableEntity, "Validation failed: Text can't be blank");
 			var mediaIds = asked.MediaIds.Distinct().ToList();
 			if (mediaIds.Count > 4 || mediaIds.Count > 0 && await DB.Default.CountAsync<Models.Media.MediaAttachment>(
-					m => mediaIds.Contains(m.ID) && m.OwnerAvatarId == MyId && m.PostId == null && m.ScheduledStatusId == null, token) != mediaIds.Count)
+					m => mediaIds.Contains(m.ID) && m.OwnerAvatarId == MyId && m.PostId == null && m.ScheduledStatusId == null
+					&& m.TrashedAt == null && m.ProfileOfAvatarId == null, token) != mediaIds.Count)
 				return Error(StatusCodes.Status422UnprocessableEntity, "Validation failed: Media attachments are not yours, already posted or too many");
 
 			var scheduled = new ScheduledStatus { AvatarId = MyId, ScheduledAt = at, Params = asked };