Refactor docker compose exec usage

Introduce centralized variables:
- docker_compose_command_base
- docker_compose_command_exec

Replaced hardcoded 'docker compose exec' with '{{ docker_compose_command_exec }}'
across multiple roles (BigBlueButton, EspoCRM, Friendica, Listmonk, Mailu, Matrix, OpenProject).
Ensures consistent environment file loading and reduces duplicated code.

Details: https://chatgpt.com/share/68d6a276-19d0-800f-839d-d191d97f7c41

roles/web-app-espocrm/tasks/01_patch_config.yml

@@ -37,7 +37,7 @@
 
 - name: Ensure siteUrl matches canonical domain
   ansible.builtin.shell: |
-    docker compose exec -T web php -r '
+    {{ docker_compose_command_exec }} -T web php -r '
       require "/var/www/html/bootstrap.php";
       $app = new \Espo\Core\Application();
       $c   = $app->getContainer();