Initial listmonk role: eom.dev newsletter on Kubernetes

listmonk v6.2.0 with PostgreSQL 17, Dex login for listed admins,
delivery through postfix.eom.dev, Catppuccin public pages, Altcha
captcha and a double opt-in "eom.dev" list. Database-held settings
are converged by an idempotent SQL script, tested against v6.2.0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

playbooks/listmonk.yaml

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: MIT-0
+# eom.dev deployment. Copy of software-infrastructure/listmonk.yaml.
+- name: Deploy listmonk
+  hosts: alpha-control-plane
+  become: true
+  vars_files:
+    - ../secrets.yaml
+  roles:
+    - role: ericomeehan.listmonk
+      # listmonk_admin_password and listmonk_smtp_password come from Vault as-is.
+      vars:
+        listmonk_db_password: "{{ listmonk_postgresql_password }}"
+        listmonk_oidc_client_secret: "{{ listmonk_dex_client_secret }}"