feat(dashboard): SSL card expired/expiring split + HAProxy frontend labels

Expired certs now show a red error alert ("renew immediately") instead
of being silently folded into the orange "expiring soon" warning.
HAProxy frontend technical names (public_http, public_https, mgmt_https)
now display as human-readable labels (HTTP In, HTTPS In, Management).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

management-ui/src/i18n/locales/en/common.json

@@ -745,6 +745,7 @@
     "sslCard": {
       "title": "SSL certificates",
       "total": "Managed certificates",
+      "certExpired": "{{count}} certificate(s) expired — renew immediately",
       "expiringSoon": "{{count}} expiring soon (< 30 days)",
       "allFresh": "All certs have > 30 days remaining."
     },