Scheduled posts: written now, published at their time

POST /api/v1/statuses with scheduled_at no longer posts at once: the post is
kept as asked (at least five minutes ahead; 300 waiting, 25 a day, as
Mastodon allows), its media kept from the janitor, and a PublishScheduled job
publishes it at its time as the persona. scheduled_statuses lists, moves and
drops them; a moved post's old job finds it not due. Idempotency-Key holds
for scheduling too.

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

PrivaPub/Domain/Media/MediaProxy.cs

@@ -157,11 +157,11 @@ namespace PrivaPub.Domain.Media
 			}
 		}
 
-		//one pass: uploads left unattached for a day go, then the proxy cache is trimmed to its size, oldest first
+		//one pass: uploads left unattached for a day go (unless a scheduled post waits for them), then the proxy cache is trimmed to its size, oldest first
 		public async Task Sweep(CancellationToken token)
 		{
 			var cutoff = DateTime.UtcNow - UnattachedLifetime;
-			foreach (var stale in await DB.Default.Find<MediaAttachment>().Match(m => m.PostId == null && m.CreatedAt < cutoff).Limit(500).ExecuteAsync(token))
+			foreach (var stale in await DB.Default.Find<MediaAttachment>().Match(m => m.PostId == null && m.ScheduledStatusId == null && m.CreatedAt < cutoff).Limit(500).ExecuteAsync(token))
 				await _media.Delete(stale);
 			TrimProxyCache();
 		}