feat: add sorting, total count and book(id) to the GraphQL API

[johahor]

The frontend needs three things from the API before it can replace Open Library:

• searchBooks has no orderBy, so limit/offset pagination can repeat or skip books between pages.
• The frontend needs the total number of matches to show pagination, so searchBooks should return { books, totalCount }.
• The details page needs a book(id) query.