feat(ansible): idempotent role-based host config for both production VMs

common/firewall/docker-tls/platform/lab-host/monitoring-agent/backup roles,
orchestrated by site.yml with the ordering that matters (firewall/TLS land
before the services that depend on them). Ansible Vault for secrets, no new
tool introduced for this project's modest secret surface. Explicit
dev/staging/production environment separation, no secrets committed
(.gitignore covers vault plaintext, TLS keys, Terraform state, *.env).

Validated: ansible-playbook --syntax-check clean.

infra/ansible/ansible.cfg

@@ -0,0 +1,10 @@
+[defaults]
+inventory = inventory/production.ini
+roles_path = roles
+host_key_checking = True
+retry_files_enabled = False
+stdout_callback = yaml
+
+[privilege_escalation]
+become = True
+become_method = sudo