Refactor async task handling

- Standardize async/poll usage with 'ASYNC_ENABLED | bool'
- Add async/poll parameters to Cloudflare, Nginx, Mailu, MIG, Nextcloud, and OpenLDAP tasks
- Update async configuration in 'group_vars/all/00_general.yml' to ensure boolean evaluation
- Allow CAA, cache, and DNS tasks to run asynchronously when enabled

https://chatgpt.com/share/689cd8cc-7fbc-800f-bd06-a667561573bf

roles/srv-web-7-7-letsencrypt/tasks/01_set-caa-records.yml

@@ -19,4 +19,6 @@
     state:    present
   loop: "{{ base_sld_domains | product(caa_entries) | list }}"
   loop_control:
-    label: "{{ item.0 }} → {{ item.1.tag }}"
+    label: "{{ item.0 }} → {{ item.1.tag }}"
+  async: "{{ ASYNC_TIME if ASYNC_ENABLED | bool else omit }}"
+  poll:  "{{ ASYNC_POLL if ASYNC_ENABLED | bool else omit }}"