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/README.md

@@ -0,0 +1,49 @@
+# fleet/data — in-cluster data tier
+
+PostgreSQL 16 (Authentik + OCIS), MongoDB 7 (portal/platform-api) and Redis 7
+(cache/sessions) as single-node StatefulSets on **Longhorn** volumes
+(`storageClassName: longhorn` — see `../longhorn/`), in the `dezky-data`
+namespace. Mirrors the dev docker-compose stack. Self-hosted on the box — no
+external/managed DBs (EU-sovereign).
+
+> Prereq: Longhorn must be installed and its `longhorn` StorageClass present
+> before applying these (the PVCs request it). See `../longhorn/README.md`.
+
+Stable in-cluster DNS:
+- `postgres.dezky-data.svc.cluster.local:5432`
+- `mongo.dezky-data.svc.cluster.local:27017`
+- `redis.dezky-data.svc.cluster.local:6379`
+
+## Apply
+
+```bash
+# 1) Secrets first (out-of-band — NOT in git). Generate values with openssl.
+cp secrets.example.yaml /tmp/data-secrets.yaml
+$EDITOR /tmp/data-secrets.yaml         # fill every REPLACE_* (openssl rand -hex 24)
+kubectl create namespace dezky-data --dry-run=client -o yaml | kubectl apply -f -
+kubectl apply -f /tmp/data-secrets.yaml && rm /tmp/data-secrets.yaml
+
+# 2) The data tier
+kubectl apply -k .
+
+# 3) Watch them come up
+kubectl -n dezky-data rollout status statefulset/postgres
+kubectl -n dezky-data rollout status statefulset/mongo
+kubectl -n dezky-data rollout status statefulset/redis
+kubectl -n dezky-data get pods,pvc
+```
+
+## Notes
+- **Postgres init runs once** (empty data dir): `postgres-init` ConfigMap
+  creates the `authentik` + `ocis` databases/roles using
+  `AUTHENTIK_DB_PASSWORD` / `OCIS_DB_PASSWORD` from the secret. If you change
+  those passwords later, alter the roles in SQL — re-init won't re-run on an
+  existing volume.
+- Store all generated passwords in **Bitwarden**. `AUTHENTIK_DB_PASSWORD` /
+  `OCIS_DB_PASSWORD` must match what you later give Authentik and OCIS.
+- **Backups:** Longhorn snapshots + backs these volumes up to Hetzner Object
+  Storage (S3) — see `../longhorn/README.md`. Block snapshots of a live DB are
+  crash-consistent at best, so also run `pg_dump`/`mongodump` CronJobs (added
+  next) into a Longhorn PVC; restore from those logical dumps, not the raw
+  data dirs.
+- Single replica each — fine for one node. HA/replicas are a later concern.