feat: deploy n8n on the cluster

The runtime for the estate's autonomous agents. Postgres as a StatefulSet with
its own claim, n8n behind a cert-manager certificate and the nginx ingress, and
both secrets in Vault behind an AppRole scoped to n8n/* alone.

The certificate is issued into the cluster rather than copied into the repo, so
the private key never reaches git. The CA certificate is committed and mounted
as NODE_EXTRA_CA_CERTS, so a workflow can reach keycloak and the domain
gateways without anyone disabling verification to make it work.

One replica and strategy: Recreate, both deliberate — n8n needs Redis and queue
mode before a second scheduler is safe, and a ReadWriteOnce volume deadlocks a
rolling update.

N8N_ENCRYPTION_KEY is generated once and kept in Vault. Regenerating it does not
re-encrypt the stored credentials, it orphans them.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

k8s/kustomization.yaml

@@ -0,0 +1,15 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+  - namespace.yaml
+  - ca-configmap.yaml
+  - secrets/clustersecretstore.yaml
+  - secrets/externalsecret.yaml
+  - postgres/statefulset.yaml
+  - postgres/service.yaml
+  - n8n/pvc.yaml
+  - n8n/configmap.yaml
+  - n8n/deployment.yaml
+  - n8n/service.yaml
+  - ingress/certificate.yaml
+  - ingress/ingress.yaml