-- Tracks the moment the user's profile cover was last (re)written on disk.
--
-- Same role and semantics as `avatar_updated_at`:
--   NULL → no custom cover; UI falls back to <AVATAR_PUBLIC_URL>/user/default-cover.webp.
--   DATE → user uploaded a cover; value doubles as a `?v=<unix-ts>` cache-buster.
--
-- Sits next to `avatar_updated_at` for tidy SHOW COLUMNS output.

ALTER TABLE `user`
    ADD COLUMN `cover_updated_at` DATETIME NULL DEFAULT NULL AFTER `avatar_updated_at`;
