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-nextcloud/tasks/04_system_config.yml

@@ -18,5 +18,5 @@
     ( ((syscfg_shell.stdout | default('')) ~ (syscfg_shell.stderr | default(''))) 
       is search(' set to ') )
   failed_when: not ASYNC_ENABLED and syscfg_shell.rc != 0
-  async: "{{ ASYNC_TIME if ASYNC_ENABLED else omit }}"
-  poll:  "{{ ASYNC_POLL if ASYNC_ENABLED else omit }}"
+  async: "{{ ASYNC_TIME if ASYNC_ENABLED | bool else omit }}"
+  poll:  "{{ ASYNC_POLL if ASYNC_ENABLED | bool else omit }}"