v2.5.5 - Bootstrap safety guards
Fix: v2.5.4 update could cause a critical error (WSOD) if PUC delivered a partial update without the new bricks-helpers.php file. Bootstrap now uses file_exists() guards on every require_once and function_exists() wrappers on helper definitions. Missing files surface as admin notices instead of fatal errors. Verified with PHP 8.2 lint + functional smoke tests before release.