refactor: simplify stack templates, move vars into group_vars/alpina

this vault setup for injective sensitive variables uses the approach described in https://docs.ansible.com/ansible/10/tips_tricks/ansible_tips_tricks.html#keep-vaulted-variables-safely-visible

roles/docker_host/tasks/main.yml

@@ -58,7 +58,7 @@
 
 - name: Clean alpina directory
   file:
-    path: "{{ my_svc_path }}"
+    path: "{{ alpina_svc_path }}"
     state: absent
   when: clean_desired is true