Add primary (write) Services to the authoritative + externaldns clusters

Writes (RFC2136/nsupdate) must hit pod-0; the round-robin read Service
would land them on a secondary. Add a dedicated write endpoint per
cluster (operator v0.1.5 primaryService field).

- bind-authoritative: LoadBalancer write endpoint on 198.18.200.9
- bind-externaldns: ClusterIP write endpoint (in-cluster writers)
- regenerate bindcluster kubeconform schema (primaryService +
  externalTrafficPolicy)

external-dns is NOT yet repointed at bind-externaldns-primary: it
authenticates with the existing key, which the operator-generated key
doesn't match until the planned Vault-sync / secret-reflection features
land.

apps/base/bind-internal/authoritative/cluster.yaml

@@ -23,6 +23,12 @@ spec:
       purelb.io/service-group: common
       purelb.io/addresses: 198.18.200.6
       external-dns.alpha.kubernetes.io/hostname: bind-authoritative.k8s.syd1.au.unkin.net
+  primaryService:
+    type: LoadBalancer
+    annotations:
+      purelb.io/service-group: common
+      purelb.io/addresses: 198.18.200.9
+      external-dns.alpha.kubernetes.io/hostname: bind-authoritative-primary.k8s.syd1.au.unkin.net
   resources:
     requests:
       cpu: 100m

apps/base/bind-internal/externaldns/cluster.yaml

@@ -19,6 +19,8 @@ spec:
       purelb.io/service-group: common
       purelb.io/addresses: 198.18.200.8
       external-dns.alpha.kubernetes.io/hostname: bind-externaldns.k8s.syd1.au.unkin.net
+  primaryService:
+    type: ClusterIP
   resources:
     requests:
       cpu: 100m