Pin binddns-externaldns service to a dedicated IP

DNS (UDP/53) can't route via a shared gateway yet (no UDPRoute), so the
service needs its own LoadBalancer address instead of a pool-assigned one.

- pin purelb.io/addresses 198.18.200.8 (common pool); move service-group dmz -> common

apps/base/binddns-externaldns/cluster.yaml

@@ -6,7 +6,7 @@ apiVersion: bind.unkin.net/v1alpha1
 kind: BindCluster
 metadata:
   name: externaldns
-  namespace: ns-externaldns
+  namespace: binddns-externaldns
 spec:
   mode: authoritative
   replicas: 3
@@ -17,7 +17,7 @@ spec:
     annotations:
       purelb.io/service-group: common
       purelb.io/addresses: 198.18.200.8
-      external-dns.alpha.kubernetes.io/hostname: ns-externaldns.k8s.syd1.au.unkin.net
+      external-dns.alpha.kubernetes.io/hostname: ns-ext.k8s.syd1.au.unkin.net
   resources:
     requests:
       cpu: 100m

apps/base/binddns-externaldns/namespace.yaml

@@ -2,4 +2,4 @@
 apiVersion: v1
 kind: Namespace
 metadata:
-  name: ns-externaldns
+  name: binddns-externaldns

apps/base/binddns-externaldns/tsigkey.yaml

@@ -5,6 +5,6 @@ apiVersion: bind.unkin.net/v1alpha1
 kind: BindTSIGKey
 metadata:
   name: externaldns-key
-  namespace: ns-externaldns
+  namespace: binddns-externaldns
 spec:
   algorithm: hmac-sha256

apps/overlays/au-syd1/binddns-externaldns/kustomization.yaml

@@ -3,4 +3,4 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 
 resources:
-  - ../../../base/ns-externaldns
+  - ../../../base/binddns-externaldns