feat: task trash, triage trash and retention settings for every area; admin can forbid keeping things for good

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/storage/tasklists.go

@@ -549,6 +549,8 @@ func (s *Store) DeleteTaskList(userID, listID string) error {
 	// The tasks stay (as personal tasks of their owners), shares and the list go – all or nothing
 	if err := s.execInTx(
 		stmt(`UPDATE thoughts SET task_list_id = '' WHERE task_list_id = ?`, listID),
+		// Its trashed tasks likewise land in their creators' own trash
+		stmt(`UPDATE trashed_tasks SET task_list_id = '', owner_id = user_id WHERE task_list_id = ?`, listID),
 		stmt(`DELETE FROM task_list_shares WHERE task_list_id = ?`, listID),
 		stmt(`DELETE FROM task_lists WHERE id = ? AND user_id = ?`, listID, userID),
 	); err != nil {