fix(settings): open the docs pages themselves, not their old addresses

The integration runbooks, the Garmin note, the guardian note on a managed
record's connections, the backups admin link and the README's self-hosting
link all pointed at retired docs paths that only resolve through redirects
(or not at all, on a host without them). They now go to the final guide
pages, and the settings tests assert the new addresses.

src/components/admin/backups-section.tsx

@@ -98,7 +98,7 @@ export function BackupsSection() {
             {/* External docs link — `noopener noreferrer` because this
                 leaves the admin shell. */}
             <a
-              href="https://docs.healthlog.dev/admin/backups"
+              href="https://docs.healthlog.dev/guides/backups/"
               target="_blank"
               rel="noopener noreferrer"
               className="text-primary inline-flex items-center gap-1 underline-offset-2 hover:underline"