feat(deploy): Ansible provisioning for prod hosts (Stage 18)

Idempotent playbooks under deploy/ansible/ prepare both production hosts:
docker-ce + compose plugin, a non-sudo deploy service account holding the CI
deploy key, key-only sshd, default-deny ufw, fail2ban, unattended upgrades and
chrony. The main host also opens 80/443/9443 and creates the external edge
network; the tg host verifies direct Bot API egress (the no-VPN assumption).

The application is deployed separately by the prod-deploy workflow (later
phase), running as the deploy account this playbook provisions.

deploy/ansible/group_vars/all.yml

@@ -0,0 +1,21 @@
+---
+# Service account the CI prod-deploy workflow uses to drive docker on the hosts.
+# Membership in the docker group is root-equivalent (docker socket access), which
+# is all the deploy workflow needs; the account is deliberately not given sudo.
+deploy_user: deploy
+
+# Public half of the dedicated CI deploy SSH key, read from the controller at run
+# time. The private half is generated on the controller during provisioning and
+# stored ONLY in the Gitea PROD_SSH_KEY secret; it is never committed. Override the
+# path with -e deploy_ci_pubkey_path=/path/to/key.pub if the key lives elsewhere.
+deploy_ci_pubkey_path: "{{ lookup('env', 'HOME') }}/.ssh/scrabble_ci_deploy_ed25519.pub"
+deploy_ci_pubkey: "{{ lookup('file', deploy_ci_pubkey_path) }}"
+
+# Base directory the deploy workflow rsyncs compose files, config, certs and dumps
+# into. Owned by deploy_user so the workflow needs no elevation.
+scrabble_base_dir: /opt/scrabble
+
+# Docker daemon json-file log rotation, mirroring the compose x-logging anchor so
+# the host's own containers (and any ad-hoc runs) rotate identically.
+docker_log_max_size: "10m"
+docker_log_max_file: "3"