Convert remaining writeShellScript usages to writeShellApplication for
shellcheck validation and strict bash options.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Replace sops-nix secrets with OpenBao vault secrets across all hosts.
Hardcode root password hash, add extractKey option to vault-secrets
module, update Terraform with secrets/policies for all hosts, and
create AppRole provisioning playbook.
Hosts migrated: ha1, monitoring01, ns1, ns2, http-proxy, nix-cache01
Wave 1 hosts (nats1, jelly01, pgdb1) get AppRole policies only.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
