Remove central Art bootstrap usage from module entrypoints

[fiammybe]

Stop loading the legacy Art framework from core bootstrap files like icms_version.php, header.php, and include/functions.ini.php.

Checklist:

• Remove direct Art includes from src/icms_version.php, src/header.php, and src/include/functions.ini.php
• Deprecate/remove iforum_load_object()
• Refactor to rely on new module helper/bootstrap
• Leave any temporary Art->IPF shims in place only where absolutely required
• Verify module and front-end still loads and functions as before