Add optional library_id query parameter support to GetCollections and
GetCollection API handlers for library-scoped book filtering.
GetCollections (GET /api/collections?library_id=X):
- When library_id is provided, include per-library book_count in the
response by querying GetCollectionItemsForDashboard for each collection
- When omitted, returns all collections as before (backward compatible)
- Added BookCount field to CollectionResponse struct
GetCollection (GET /api/collections/:id?library_id=X):
- System collections (non-empty QueryType): uses DashboardService to
fetch library-scoped sections, matching the existing SSR handler logic
- User collections: uses GetCollectionItemsForDashboard for
library-filtered results, excluding soft-deleted items
- When library_id is omitted, returns all books as before
john-okeefe
faef4d9fff