docs: add portable from-zero deploy runbook and GitOps templates

Document server-side rollout (values, Sealed Secrets, logging, greenfield
reset) with environment variables so any cluster can follow the same steps.

Co-authored-by: Cursor <cursoragent@cursor.com>

gitops/sealed-secrets/elasticsearch-credentials.example.yaml

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+# Example: seal Elasticsearch stack credentials (namespace logging).
+# Full guide (any environment): RUNBOOK-DEPLOY.fa.md — Phase 4
+# Apply elasticsearch-stack.yaml FIRST (without inline passwords), then create this Secret.
+#
+#   kubectl -n logging create secret generic elasticsearch-credentials \
+#     --from-literal=ELASTIC_PASSWORD="$(openssl rand -base64 24)" \
+#     --from-literal=FLUENTBIT_PASSWORD="$(openssl rand -base64 24)" \
+#     --dry-run=client -o json \
+#   | kubeseal \
+#       --controller-name=sealed-secrets-controller \
+#       --controller-namespace=kube-system \
+#       --format yaml \
+#   > ../cloud-host-gitops/sealed-secrets/elasticsearch-credentials.yaml
+#
+# Backend must receive the same ELASTIC_* values via backend.env in values-abrban.yaml
+# (or a separate SealedSecret referenced with envFrom).
+#
+# After deploy, verify:
+#   kubectl -n logging get secret elasticsearch-credentials
+#   curl -u elastic:$ELASTIC_PASSWORD https://elasticsearch.logging.svc.cluster.local:9200