feat(domains): surface autodiscovery SRV records (RFC 6186)

Mail clients could never autoconfigure: Stalwart's zone file contains the
_imaps/_submissions/_pop3s SRV records but classify() dropped everything
except mx/spf/dkim/dmarc, so customers never saw them and every client
needed manual server entry. New 'autodiscovery' record kind: classified
from the zone (only the services actually reachable in prod — the
_jmap/_caldavs SRVs target :443 which Traefik owns, deferred to the
webmail story), verified via resolveSrv (missing=bad, wrong target=warn),
shown as an OPTIONAL slot on the portal Domains page that never gates the
domain status or the records-to-fix nag.

Also fixed on the live server via management JMAP (x:SystemSettings):
hostname was the machine name node1.dezky.eu from the v0.16 auto-bootstrap
— MX/SRV targets and the SMTP banner now say mail.dezky.eu, and the LE
x:Certificate is set as defaultCertificateId.

apps/portal/composables/useDomains.ts

@@ -6,7 +6,7 @@
 
 export type RecordStatus = 'ok' | 'warn' | 'bad' | 'pending'
 export type DomainStatus = 'pending' | 'verifying' | 'active' | 'error'
-export type RecordKind = 'ownership' | 'mx' | 'spf' | 'dkim' | 'dmarc'
+export type RecordKind = 'ownership' | 'mx' | 'spf' | 'dkim' | 'dmarc' | 'autodiscovery'
 export type DmarcPolicy = 'none' | 'quarantine' | 'reject'
 
 export interface DomainRecordView {