Make DNS servers fully dynamic from config.json

DNS server IDs (dns1, dns2, dns3) were hardcoded throughout the frontend
and backend. Now config.json's dnsServers object is the single source of
truth — adding or removing a DNS server in config automatically updates
the dashboard cards, credential modal, health checks, and probes.

- credentials.js: rebuild modal sections dynamically from SITE.dnsServers
- globals.js: add getPrimaryDnsId() helper for primary DNS lookups
- service-create.js, service-infrastructure.js: use dynamic DNS ID
- startup-validator.js: dynamic topCardServices from config
- middleware.js: add license endpoints to public routes

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

status/js/core/service-infrastructure.js

@@ -146,7 +146,7 @@
   // ===== CREATE DNS RECORD =====
 
   async function createDnsRecord(subdomain, ip, ttl = DC.DEFAULTS.TTL) {
-    const dnsToken = window.getToken('dns2', 'admin');
+    const dnsToken = window.getToken(getPrimaryDnsId(), 'admin');
 
     if (!dnsToken) {
       throw new Error('DNS admin token not configured. Please set it in the Tokens menu.');