Add Book model

models/book.py

@@ -0,0 +1,20 @@
+from sqlalchemy import Column, String, Integer, DateTime, ForeignKey
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+from core.database import Base
+import uuid
+
+class Book(Base):
+    __tablename__ = "books"
+    
+    id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
+    title = Column(String, nullable=False, index=True)
+    description = Column(String)
+    isbn = Column(String, unique=True)
+    publication_year = Column(Integer)
+    author_id = Column(String, ForeignKey("authors.id"), nullable=False)
+    
+    author = relationship("Author", back_populates="books")
+    
+    created_at = Column(DateTime, default=func.now())
+    updated_at = Column(DateTime, default=func.now(), onupdate=func.now())