SQLite `books` persistence via `app.persistence.get_book_store()`: - `BookStore.add(title, author) -> Book` - `BookStore.list_ordered() -> list[Book]` - `BookStore.remove(book_id) -> bool` - Schema: `id`, required `title`, required `author`, `created_at`; insertion order follows ascending SQLite primary key. - Initialization is idempotent and preserves rows. - SQLite access remains encapsulated; connections are scoped to Flask application contexts. - Empty titles/authors are rejected and never stored.