first implementation

backend/src/main/java/com/aiteacher/book/BookRepository.java

@@ -0,0 +1,15 @@
+package com.aiteacher.book;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+import java.util.List;
+import java.util.UUID;
+
+@Repository
+public interface BookRepository extends JpaRepository<Book, UUID> {
+
+    List<Book> findByStatus(BookStatus status);
+
+    boolean existsByStatus(BookStatus status);
+}