Switch from homelab.local to coreworlds.io with split-horizon DNS and LAN-only access controls

- Migrate all ingress hostnames from *.homelab.local to *.coreworlds.io
- Remove broken Traefik certresolver config (cert-manager handles TLS)
- Add internal-only IP allowlist middleware for platform services
- Add IngressRoutes for ArgoCD, Grafana, Longhorn (LAN-only via middleware)
- Seal and add Cloudflare API token for cert-manager DNS-01 challenges
- Update cert-manager ClusterIssuers with real email
- Update k3s TLS SAN to k3s.coreworlds.io
- Rewrite Ubiquiti docs for single-node topology and split-horizon DNS
- Fix seal-secret.sh controller name to match Helm release
- Add UCG DNS setup script using API key auth

infra/kubernetes/platform/cert-manager-config/clusterissuer-letsencrypt.yaml

@@ -9,7 +9,7 @@ metadata:
 spec:
   acme:
     server: https://acme-staging-v02.api.letsencrypt.org/directory
-    email: admin@homelab.local
+    email: julia.eloise@pm.me
     privateKeySecretRef:
       name: letsencrypt-staging-key
     solvers:
@@ -26,7 +26,7 @@ metadata:
 spec:
   acme:
     server: https://acme-v02.api.letsencrypt.org/directory
-    email: admin@homelab.local
+    email: julia.eloise@pm.me
     privateKeySecretRef:
       name: letsencrypt-production-key
     solvers: