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/traefik/kustomization.yaml

@@ -3,3 +3,7 @@ kind: Kustomization
 resources:
   - helmchartconfig.yaml
   - middleware-default-headers.yaml
+  - middleware-internal-only.yaml
+  - ingressroute-argocd.yaml
+  - ingressroute-grafana.yaml
+  - ingressroute-longhorn.yaml