_start_cleanup_scheduler and _cleanup_old_data move verbatim to modules/web_viewer/cleanup.py (AST-identical; the other 23 BotDataViewer methods are unchanged). app.py keeps importing delete_timestamp_rows_in_chunks and retention_delete_settings so modules.web_viewer.app still exposes them; as with the earlier mixins, patching those names on app no longer reaches the moved code. app.py is 4,808 lines.
