Add data retrieval helpers for SSR template rendering:
- GetDeviceMappingsData: Fetch device shelf mappings for device settings UI
- GetUserCollectionsList: Get all user collections for dropdowns and listings
- GetCollectionData: Get single collection with metadata
- GetCollectionBooksData: Get books in a collection
These functions support the Phase 9 frontend features by providing
efficient data access for template rendering without modifying
existing API endpoints.
- Add OPDS handler for device catalog and book downloads
- Add collections handler for collection CRUD
- Add book matching service for cross-device book linking
- Add sidecar handler for Kobo metadata sync
- Add sync handler for device synchronization
john-okeefe