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.

.gitignore

@@ -5,6 +5,18 @@ drb-server-discord-bot/.env
 drb-frontend/.env
 drb-c2-core/gcp-key.json
 
+# Terraform
+infra/.terraform/
+infra/terraform.tfstate
+infra/terraform.tfstate.backup
+infra/terraform.tfstate.*.backup
+infra/.terraform.lock.hcl
+infra/terraform.tfvars
+infra/tf.log
+infra/ansible/inventory.ini
+infra/ansible/group_vars/all.yml
+infra/ansible/vault.yml
+
 # Python
 __pycache__/
 *.py[cod]