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/web-app-mig/tasks/02_build_data.yml

@@ -3,8 +3,8 @@
     set -euo pipefail
     infinito build tree --no-signal --alarm-timeout 0 -s {{ mig_roles_meta_volume }}
     infinito build roles_list --no-signal --alarm-timeout 0 -o {{ mig_roles_meta_list }}
-  async: "{{ (3600 if ASYNC_ENABLED else omit) | default(omit) }}"
-  poll:  "{{ ASYNC_POLL if ASYNC_ENABLED else omit }}"
+  async: "{{ (3600 if ASYNC_ENABLED | bool else omit) | default(omit) }}"
+  poll:  "{{ ASYNC_POLL if ASYNC_ENABLED | bool else omit }}"
   register: mig_build_job
 
 - name: Fail if MIG build job did not start