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/fr.ts

@@ -1718,6 +1718,11 @@ export const catalog: Catalog = {
     "To confirm, type {phrase}": "Pour confirmer, saisissez {phrase}",
     "Turn off legacy protocols": "Désactiver les protocoles de messagerie historiques",
     "Legacy mail protocols are off for your organization. Only {app} and JMAP apps can sign in.": "Les protocoles de messagerie historiques sont désactivés pour votre organisation. Seuls {app} et les applications JMAP peuvent se connecter.",
+    // ── About: webmail and mail server nodes (inbuxa) ──────────────
+    "Webmail node": "Nœud du webmail",
+    "Mail server node": "Nœud du serveur de messagerie",
+    "{host} does not resolve": "{host} ne se résout pas",
+    "unavailable": "indisponible",
     // ── Spam filter: the language model's opinion (inbuxa) ──────────
     "Language model's opinion": "Avis du modèle de langage",
     "One of several signals the spam filter weighed": "Un signal parmi d'autres pris en compte par le filtre antispam",