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/ru.ts

@@ -1715,6 +1715,11 @@ export const catalog: Catalog = {
     "To confirm, type {phrase}": "Для подтверждения введите {phrase}",
     "Turn off legacy protocols": "Отключить устаревшие почтовые протоколы",
     "Legacy mail protocols are off for your organization. Only {app} and JMAP apps can sign in.": "Устаревшие почтовые протоколы отключены для вашей организации. Входить могут только {app} и приложения JMAP.",
+    // ── About: webmail and mail server nodes (inbuxa) ──────────────
+    "Webmail node": "Узел веб-почты",
+    "Mail server node": "Узел почтового сервера",
+    "{host} does not resolve": "{host} не разрешается",
+    "unavailable": "недоступно",
     // ── Spam filter: the language model's opinion (inbuxa) ──────────
     "Language model's opinion": "Мнение языковой модели",
     "One of several signals the spam filter weighed": "Один из нескольких признаков, которые учёл спам-фильтр",