docs: deployement guide with new ui update settings

docs/configuration.md

@@ -34,6 +34,8 @@ Copy [`.env.example`](../.env.example) to `.env` to get started. When a required
 
 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).
+
 ## Adding a variable
 
 1. Read it in the code where it is needed (infrastructure or `api/`, never `internal/domain`).