Backups & restore

Backups are a VACUUM INTO SQLite snapshot streamed straight into a ZIP and then into storage (local or S3) without ever buffering the whole archive in memory — verified on a 1.6 GB database peaking at ~330 MB RSS. The dashboard’s Backups page can trigger, list, download, and restore a backup. One conformance test against the real PocketBase SDK suite is skipped specifically because it restarts the server mid-run to exercise restore, which would kill the test harness itself — see KNOWN_DIVERGENCES.md.