notification-mail-recheck: Re-check DNS on Server › Settings

The owner, 2026-10-16: "Да, бери notification-mail-recheck". The records
of the server's own name can be checked again where they are shown: Re-
check DNS in Settings' page head (mockup 98e4dfc) posts to
POST /server/settings/dns-recheck (guard 52a9811), global role, which
runs Health's lookups - the server's address, then serverMail(true) - and
returns to /server/settings?rechecked=1, "DNS re-checked.". The
Notification mail box's end slot says when the records were checked
("The server's own name · checked 3 min ago", from the check's
CheckedAt; the old wording while nothing was looked up). A record that
has turned right comes back folded.

Tests: the page head's form and the end slot, and the Settings form
holding neither the re-check nor the right column
(TestSettingsRechecksTheMailRecords); the re-check skips the cache,
redirects and the page shows both records folded
(TestSettingsRecheckAsksForNotificationMailAgain); a domain
administrator gets 404 (globalOnlyRoutes). go vet + go test (26
packages) and make e2e on the test server for this tree.

Docs: architecture.md routes, the panel-redesign plan's route table,
guide § Settings, help (help.go word for word with the mockup's);
CHANGELOG [Unreleased]; roadmap row done. The roadmap's settings-save-row
note no longer claims the left-column form was needed for this - the
action went to the page head.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/guide.md

@@ -551,7 +551,9 @@ prune cycle without a container restart), and, read-only, the level-1 rate
 limit that comes from `.env` ([Rate limiting — level 1](#rate-limiting--level-1-ip-backstop)).
 There is no panel-wide DMARC report address: each domain has its own. The page
 also has the switch for [notifications](#notifications) and the two DNS records
-that make them arrive.
+that make them arrive, with when they were last checked; **Re-check DNS** at
+the top of the page checks them again once they are published (results are
+otherwise kept a few minutes).
 
 ### Notifications