## 1. Variable Migration

- [x] 1.1 Remove `trojan_domain` and `certbot_email` from `group_vars/all.yml` (or set to empty strings as fallback defaults)
  - *Note: Variables already defined as empty strings in `roles/trojan/defaults/main.yml`, no change needed in `group_vars/all.yml`.*

## 2. Inventory Update

- [x] 2.1 Update `inventory/hosts.yml.example` to show per-host `trojan_domain` and `certbot_email` configuration

## 3. Role Validation

- [x] 3.1 Add `assert` task in `roles/trojan/tasks/main.yml` to fail early if `trojan_domain` or `certbot_email` is undefined/empty
- [x] 3.2 Verify all existing `trojan_domain` and `certbot_email` references in trojan role work correctly with host variables
  - *Note: All references use `{{ trojan_domain }}` and `{{ certbot_email }}`, Ansible variable resolution automatically handles host variables without code changes.*

## 4. Documentation

- [x] 4.1 Update `README.md` configuration section to reflect per-host domain setup

## 5. Validation

- [x] 5.1 Run `ansible-playbook --syntax-check` to validate playbook integrity