refactor(web-app-mediawiki): unify debug & oidc handling via _ensure_require, introduce host-side prep, switch to bind mounts

- Removed obsolete Installation.md, TODO.md, 02_debug.yml, 05_oidc.yml and legacy debug enable/disable tasks
- Added 01_prep.yml to render debug.php/oidc.php on host side before container start
- Introduced _ensure_require.yml for generic require_once management in LocalSettings.php
- Renamed 01_install.yml -> 02_install.yml to align with new numbering
- Updated docker-compose.yml.j2 to bind-mount mw-local into /opt/mw-local
- Adjusted vars/main.yml to define MEDIAWIKI_LOCAL_MOUNT_DIR and MEDIAWIKI_LOCAL_PATH
- Templates debug.php.j2 and oidc.php.j2 now gated by MODE_DEBUG and MEDIAWIKI_OIDC_ENABLED
- main.yml now orchestrates prep, install, debug, extensions, oidc require, admin consistently

Ref: https://chatgpt.com/share/68b57db2-efcc-800f-a733-aca952298437

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

@@ -5,6 +5,7 @@
     image: "{{ MEDIAWIKI_IMAGE }}:{{ MEDIAWIKI_VERSION }}"
     volumes:
       - "data:/var/www/html/"
+      - "{{ MEDIAWIKI_LOCAL_MOUNT_DIR }}:{{ MEDIAWIKI_LOCAL_PATH }}:ro"
     ports:
       - "127.0.0.1:{{ ports.localhost.http[application_id] }}:{{ container_port }}"
 {% include 'roles/docker-container/templates/healthcheck/curl.yml.j2' %}