watchstate: expose externally at watchstate.unkin.net

Add a public front door for the WatchState admin UI on watchstate.unkin.net
via the external (DMZ) Traefik, alongside the existing internal
watchstate.k8s.syd1.au.unkin.net gateway. oauth2-proxy fronts both hostnames.

- DNSRecord watchstate-dns-internal (bind-internal/authoritative, unkin.net
  zone) -> A 198.18.199.0, the traefik-external VIP (arrstack precedent).
- watchstate-external Gateway (traefik-external) + HTTPRoutes: http->https
  redirect and https -> watchstate-oauth2:80. TLS terminated with the
  Let's Encrypt *.unkin.net wildcard (wildcard-unkin-net-tls), so no
  cert-manager/external-dns annotations.
- oauth2-proxy: relative redirect-url (/oauth2/callback) so reverse-proxy mode
  derives scheme+host per request, making the callback work on BOTH hosts;
  cookie + whitelist domains cover both hostnames.
- Drop the no-op sync-wave: "0" annotation on the vaultauth default VaultAuth.

Dependencies:
- wildcard-unkin-net-tls reflection into the watchstate namespace (reflector
  allow-list, argocd-apps PR #418).
- Both callback URIs registered on the Authentik watchstate provider
  (terraform-authentik, separate PR).

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

@@ -147,3 +147,18 @@ spec:
     # traefik-internal gateway VIP; the cheeztv Gateway serves cheeztv.unkin.net
     # there.
     - 198.18.200.4
+---
+apiVersion: bind.unkin.net/v1alpha1
+kind: DNSRecord
+metadata:
+  name: watchstate-dns-internal
+  namespace: bind-internal
+spec:
+  zoneRef: unkin-net
+  name: watchstate
+  type: A
+  ttl: 600
+  values:
+    # traefik-EXTERNAL (DMZ) gateway VIP; the watchstate-external Gateway serves
+    # the watchstate.unkin.net front door (oauth2-proxy) there.
+    - 198.18.199.0