refactor(web-app-wordpress): unify variable naming to uppercase WORDPRESS_* style

- Replaced all lowercase wordpress_* variables with uppercase WORDPRESS_* equivalents
- Ensured consistency across tasks, templates, and vars
- Improves readability and aligns with naming conventions

Conversation: https://chatgpt.com/share/68af29b5-8e7c-800f-bd12-48cc5956311c

roles/web-app-wordpress/tasks/02_install.yml

@@ -1,13 +1,13 @@
 - name: "Run WordPress core install via WP CLI"
   no_log: "{{ MASK_CREDENTIALS_IN_LOGS | bool }}"
   command: >
-    docker exec -u {{ wordpress_user }} {{ wordpress_container }}
+    docker exec -u {{ WORDPRESS_USER }} {{ WORDPRESS_CONTAINER }}
     wp core install
       --url="{{ domains | get_url(application_id, WEB_PROTOCOL) }}"
       --title="{{ applications | get_app_conf(application_id, 'title', True) }}"
       --admin_user="{{ applications | get_app_conf(application_id, 'users.administrator.username') }}"
       --admin_password="{{ applications | get_app_conf(application_id, 'credentials.administrator_password', True) }}"
       --admin_email="{{ applications | get_app_conf(application_id, 'users.administrator.email', True) }}"
-      --path="{{ wordpress_docker_html_path }}"
+      --path="{{ WORDPRESS_DOCKER_HTML_PATH }}"
   args:
     chdir: "{{ docker_compose.directories.instance }}"