Replace hardcoded sidebar drawer configuration with admin-manageable
dynamic system. Extend page_status.json with drawer definitions and
page assignments, add drawer CRUD API endpoints, render portal sidebar
via Jinja2 loops, and extend /admin/pages UI with drawer management.
Fix multi-worker cache invalidation via mtime-based staleness detection.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>