feat(infra): k3s foundation — cert-manager, Longhorn config, in-cluster data tier

Adds the production cluster foundation (authored + applied live on node1):
- cert-manager via the k3s HelmChart controller + letsencrypt staging/prod
  ClusterIssuers (HTTP-01 / Traefik).
- Longhorn config for single-node (values: replica=1, default StorageClass,
  Retain) + backup-to-Hetzner-Object-Storage credential template.
- In-cluster data tier (dezky-data): Postgres 16 (with Authentik+OCIS DB init),
  MongoDB 7, Redis 7 as StatefulSets on Longhorn, + secret template.
- bootstrap.sh: install open-iscsi/nfs-common + enable iscsid (Longhorn prereq).
- RUNBOOK.md: full reproducible node1 build order.

Real secrets are generated on-box and kept in Bitwarden — never in git.

infrastructure/production/fleet/data/kustomization.yaml

@@ -0,0 +1,12 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+namespace: dezky-data
+
+# Non-secret resources only. Real secrets (secrets.example.yaml) are applied
+# out-of-band and deliberately NOT listed here — same pattern as apps/.
+resources:
+  - namespace.yaml
+  - postgres-init.yaml
+  - postgres.yaml
+  - mongodb.yaml
+  - redis.yaml