Add metadata_refresh_mode (manual/hourly/daily/weekly) to libraries,
with automatic scheduling via the indexer. Includes API support,
backoffice UI controls, i18n translations, and DB migration.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
- Change all instances of AppState to reference the new state module across multiple files for consistency.
- Clean up imports in auth, books, index_jobs, libraries, pages, search, settings, thumbnails, and tokens modules.
- Simplify main.rs by removing unused code and organizing middleware and route handlers under the new handlers module.
