v1.7.49 - Queue and Quality Hardening

• Add checkpoint-safe pause, resume, and cancel controls to Background Queue.\n- Classify retryable failures, apply exponential backoff, and stop retrying permanent API errors.\n- Add server-side pagination, accurate queue counts, configurable retention cleanup, and worker health reporting.\n- Enforce Workflow Lab Quality Gate thresholds with administrator-only, reasoned overrides.\n- Sanitize generated HTML before persistence and final draft writes.\n- Stop rendering saved API keys in settings and support wp-config.php secret constants.\n- Add WordPress/PHP compatibility metadata, data-retention documentation, and hardening regression tests.