add Terraform + Ansible infrastructure for GCP deployment

Provisions e2-micro VM (us-east1-b, free tier) with static IP, SSH and
web firewall rules, Docker + Caddy startup script, and IAM bindings for
Firestore and GCS access via ADC. Imports existing drb-calls bucket and
c2-server Firestore database into state. Ansible roles handle first-time
setup (swap, docker group) and all subsequent deploys via rsync + docker
compose, with secrets managed via Ansible Vault. DNS stays on AWS Route 53.

infra/ansible/roles/deploy/templates/root.env.j2

@@ -0,0 +1,7 @@
+# Top-level docker-compose environment — MQTT credentials for the broker container.
+# Managed by Ansible. Do not edit manually.
+
+MQTT_C2_USER={{ vault_mqtt_c2_user }}
+MQTT_C2_PASS={{ vault_mqtt_c2_pass }}
+MQTT_NODE_USER={{ vault_mqtt_node_user }}
+MQTT_NODE_PASS={{ vault_mqtt_node_pass }}