refactor(web-app-mybb): remove obsolete Installation.md, introduce schema for secret_pin, and rework task/vars handling

- Removed outdated Installation.md (manual plugin instructions no longer needed)
- Added schema/main.yml with validation for secret_pin
- Added config.php.j2 template to manage DB + admin config
- Refactored tasks/main.yml to deploy config.php instead of legacy docker-compose
- Removed setup-domain.yml (TLS/domain handling moved to core roles)
- Updated docker-compose.yml.j2 to mount config.php and use new vars
- Cleaned up vars/main.yml: standardized MYBB_* variable names, added MYBB_SECRET_PIN, config paths, and container port

See ChatGPT conversation: https://chatgpt.com/share/68b0ae26-93ec-800f-8785-0da7c9303090

roles/web-app-mybb/templates/docker-compose.yml.j2

@@ -1,11 +1,8 @@
 {% include 'roles/docker-compose/templates/base.yml.j2' %}
   application:
-    logging:
-      driver: journald
-      options:
-        tag: "mybb_application"
-    image: {{ mybb_image }}:{{ mybb_version }}
-    container_name: {{ mybb_name }}
+{% include 'roles/docker-container/templates/base.yml.j2' %}
+    image: {{ MYBB_IMAGE }}:{{ MYBB_VERSION }}
+    container_name: {{ MYBB_CONTAINER }}
     restart: {{ DOCKER_RESTART_POLICY }}
     volumes:
       - data:/var/www/html
@@ -13,21 +10,20 @@
 {% include 'roles/docker-container/templates/networks.yml.j2' %}
 
   server:
-    logging:
-      driver: journald
-      options:
-        tag: "mybb_server"
+{% include 'roles/docker-container/templates/base.yml.j2' %}
     image: nginx:mainline
     restart: {{ DOCKER_RESTART_POLICY }}
     ports:
-      - "127.0.0.1:{{ ports.localhost.http[application_id] }}:80"
+      - "127.0.0.1:{{ ports.localhost.http[application_id] }}:{{ container_port }}"
     volumes:
-    - "{{docker_compose_instance_confd_directory}}:{{target_mount_conf_d_directory}}:ro"
+    - "{{ MYBB_NGINX_CONF_DIR_HOST }}:{{ MYBB_NGINX_CONF_DIR_DOCK }}:ro"
+    - "{{ MYBB_CONFIG_HOST_PATH }}:{{ MYBB_CONFIG_DOCK_PATH }}:ro"
     - "data:/var/www/html:ro"
+{% include 'roles/docker-container/templates/healthcheck/curl.yml.j2' %}
 {% include 'roles/docker-container/templates/networks.yml.j2' %}
 
 {% include 'roles/docker-compose/templates/volumes.yml.j2' %}
   data:
-    name: {{ mybb_volume }}
+    name: {{ MYBB_VOLUME }}
 
 {% include 'roles/docker-compose/templates/networks.yml.j2' %}