refactor(domains): Einstellung Standard-Nameserver entfernt, Doku angepasst (h3t)

- Spalte DomainsConfig.defaultNameServers per Migration 20261008160000 entfernt
- Feld in Einstellungen/Status (API, DTO, Typen) und Karte im Web entfernt
- Anleitungen und CHANGELOG: Nameserver kommen aus AutoDNS

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

apps/web/src/messages/en.json

@@ -2100,13 +2100,6 @@
         "test": "Test connection",
         "testing": "Testing connection …",
         "saveFirst": "Please save first"
-      },
-      "nameServers": {
-        "title": "Default name servers",
-        "description": "These name servers are prefilled for every registration. They must already be set up with your provider, otherwise the registration fails.",
-        "label": "Name server {number}",
-        "add": "Add name server",
-        "remove": "Remove"
       }
     },
     "common": {