Add Authentik identity provider deployment

- Helm chart authentik 2026.5.3 with 3 server replicas, 2 worker replicas
- CNPG PostgreSQL cluster (3 instances) with rw and ro poolers (2 instances each)
- Redis with 5Gi persistent storage
- Gateway API: identity.unkin.net and identity.k8s.syd1.au.unkin.net (HTTPS)
- LDAPS via TLSRoute on ldap.k8s.syd1.au.unkin.net and ldap.main.unkin.net
- Multi-SAN TLS via cert-manager gateway integration
- S3 storage via RadosGW (bucket: authentik)
- Vault secrets: postgres-credentials, authentik-credentials, s3-credentials
- Woodpecker ServiceAccount for terraform-authentik CI
- Platform applicationset and project updated

apps/base/authentik/kustomization.yaml

@@ -0,0 +1,19 @@
+---
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+  - cnpg_cluster.yaml
+  - cnpg_pooler.yaml
+  - gateway.yaml
+  - httproute.yaml
+  - ldap-gateway.yaml
+  - ldap-httproute.yaml
+  - ldap-service.yaml
+  - ldap-tlsroute.yaml
+  - namespace.yaml
+  - redis-deployment.yaml
+  - redis-pvc.yaml
+  - redis-service.yaml
+  - vaultauth.yaml
+  - vaultstaticsecret.yaml