About: name the webmail node and the mail server node

Settings > About shows which webmail node answered (NODE_NAME, else the
container hostname) and which inbuxa node it talks to: the address the
server's name resolves to from the webmail, named by its PTR record. The
server only tells administrators its node name, so the webmail works it
out itself. Fetched from /api/about/nodes on every visit, cached for a
minute server-side, for troubleshooting a cluster.

Fork-only: upstream ihasmail runs one webmail against one server.
4 new strings, translated in all 9 catalogues.

web/src/locales/es.ts

@@ -1713,6 +1713,11 @@ export const catalog: Catalog = {
     "To confirm, type {phrase}": "Para confirmar, escriba {phrase}",
     "Turn off legacy protocols": "Desactivar los protocolos de correo heredados",
     "Legacy mail protocols are off for your organization. Only {app} and JMAP apps can sign in.": "Los protocolos de correo heredados están desactivados para su organización. Solo {app} y las aplicaciones JMAP pueden iniciar sesión.",
+    // ── About: webmail and mail server nodes (inbuxa) ──────────────
+    "Webmail node": "Nodo del webmail",
+    "Mail server node": "Nodo del servidor de correo",
+    "{host} does not resolve": "{host} no se resuelve",
+    "unavailable": "no disponible",
     // ── Spam filter: the language model's opinion (inbuxa) ──────────
     "Language model's opinion": "Opinión del modelo de lenguaje",
     "One of several signals the spam filter weighed": "Una de varias señales que el filtro de spam ha tenido en cuenta",