feat: media duplicate purge, part 2 of 3: the automatic purge scheduler (Go only)

docs/configuration.md

@@ -33,6 +33,8 @@ Copy [`.env.example`](../.env.example) to `.env` to get started. When a required
 | `RENEWCMS_CONTAINER` | `false` | Set to `true` (case-insensitive; any other value means `false`) when the app runs in a container. Settings then tells the owner to update by pulling a new image instead of offering browser updates, and `can_apply` is always `false`. The Dockerfile and `docker-compose.yml` set it to `true`. Update checks still work. |
 | `UPDATE_FEED_URL`      | `https://git.floriansylvain.fr` | Base URL of the Gitea server that publishes RenewCMS releases. The Settings page asks `{UPDATE_FEED_URL}/api/v1/repos/fsylvain/RenewCMS/releases` when the owner checks for updates. The last result is kept in `update-status.json`, next to `DB_FILE`. |
 
+Automatic media purge has no environment variable. Its schedule (on or off, interval, `enabled_at`, `last_purge_at`) lives in the purge settings row of the database, is changed from the Settings page or `PATCH /v1/media/purge-settings`, and is read again at every hourly tick.
+
 Relative paths are resolved against the process's working directory. In production, use absolute paths (see [deployment.md](deployment.md)).
 
 For example, `WorkingDirectory=/var/lib/renewcms` with `DB_FILE=./data/renewcms.db` puts the database in `/var/lib/renewcms/data`. Browser-update `--data-dir` must name that directory, because the app reads helper status and update records beside the database. It is not necessarily `WorkingDirectory` or `ReadWritePaths`. Do not change an existing `DB_FILE` merely to match the helper: that could open a different, empty database. See [browser-update setup](deployment.md#browser-updates).