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/Models/Media/MediaAttachment.cs

@@ -19,6 +19,11 @@ namespace PrivaPub.Models.Media
 		public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
 		public DateTime? AttachedAt { get; set; }
 		public string ScheduledStatusId { get; set; }//kept for a scheduled post until it is published or dropped
+		public string ProfileOfAvatarId { get; set; }//a persona's avatar or header (Kind "avatar" or "header"), never a post's
+		// set once nothing holds it any more (its post deleted, edited out, replaced, its root removed, never posted): its
+		// files move out of what /media/files serves at once, and the janitor deletes them after a grace
+		public DateTime? TrashedAt { get; set; }
+		public string TrashReason { get; set; }
 	}
 
 	public class MediaSecret : Entity