@quill/db	minor
@quill/shared	minor

Revert a form to its previously published version, by API or from the editor.

Publishing directly is safe because it can be undone in one click.

• Every publish now keeps the live config it replaces (previous_config) and when that version went live (previous_published_at_ms: the last publish, or the form's creation for a form that was live before its first publish).
• POST /v1/forms/:id/revert puts the previous version back live, and the version it replaces becomes the previous, so reverting twice undoes the revert. The destinations the form has now are kept, and a pending draft is not touched. With nothing to go back to it answers 409 NOTHING_TO_REVERT. An API key may call it. The public form serves the reverted version as soon as the call returns.
• Form responses carry previousPublishedAt (epoch-ms, or null when there is nothing to revert to). The stored version itself stays on the server.
• In the editor, the Publish button gains a menu with "Revert to the previous published version". It shows when that version went live, is disabled while there is none, and asks first in a dialog that names the date and says the draft does not change.
• @quill/db gains revertForm and FormRow.previousPublishedAt; @quill/shared gains the admin.publish revert copy (EN + ES).