feat(kanidm): deploy Kanidm 1.10.3 with 2-replica replication

## Summary

- Deploys Kanidm 1.10.3 (ghcr.io/kanidm/server:1.10.3) as a 2-replica
  StatefulSet with built-in replication enabled
- Domain: auth.unkin.net (primary WebAuthn origin); au.auth.unkin.net
  is an additional hostname for this au-syd1 instance
- TLS: cert-manager Certificate (vault-issuer) covering auth.unkin.net,
  au.auth.unkin.net, kanidm.k8s.syd1.au.unkin.net, and internal
  headless pod DNS names — Kanidm terminates TLS itself (passthrough)
- Gateway: TLS passthrough on port 443 via TLSRoute; HTTP on port 80
  redirects to HTTPS; external-dns creates kanidm.k8s.syd1.au.unkin.net
  (not used in server.toml; canonical origin is auth.unkin.net only)
- Replication: init container generates per-pod server.toml with the
  correct repl:// origin (kanidm-{N}.kanidm-headless.kanidm.svc);
  populate kanidm-repl-peers ConfigMap post-deployment after running
  `kanidmd show-replication-certificate` on each pod
- Storage: 10Gi cephrbd-fast-delete PVC per pod via volumeClaimTemplates
- Security: runAsUser/runAsGroup 1000, runAsNonRoot, no privilege
  escalation, allowPrivilegeEscalation=false
- ArgoCD: platform ApplicationSet and Project updated for kanidm namespace

## Requires

- PR benvin/kanidm-artifactapi (add ^kanidm/ to ghcr immutable patterns)
  to be merged first so artifactapi can cache ghcr.io/kanidm/server

## Post-deployment steps

1. Wait for both pods to reach Running state
2. Exchange replication certificates between pods:
   kubectl exec -n kanidm kanidm-0 -- kanidmd show-replication-certificate
   kubectl exec -n kanidm kanidm-1 -- kanidmd show-replication-certificate
3. Edit kanidm-repl-peers ConfigMap with both nodes' certs
   (see template in configmap.yaml comments)
4. kubectl rollout restart statefulset/kanidm -n kanidm

## Test plan

- [x] Sandbox tested in sandbox-kanidm: all 11 resources server dry-run OK
- [ ] After merge: ArgoCD syncs kanidm namespace
- [ ] Verify auth.unkin.net and au.auth.unkin.net reachable via Gateway
- [ ] Verify kanidm.k8s.syd1.au.unkin.net DNS record created by external-dns
- [ ] Complete replication cert exchange and verify replication active

argocd/projects/platform.yaml

@@ -27,6 +27,8 @@ spec:
       server: https://kubernetes.default.svc
     - namespace: 'jfrog'
       server: https://kubernetes.default.svc
+    - namespace: 'kanidm'
+      server: https://kubernetes.default.svc
     - namespace: 'node-feature-discovery'
       server: https://kubernetes.default.svc
     - namespace: 'purelb'