first implementation - image/drawing integration

backend/src/main/java/com/aiteacher/document/ChapterEntity.java

@@ -0,0 +1,47 @@
+package com.aiteacher.document;
+
+import jakarta.persistence.*;
+import java.time.Instant;
+import java.util.UUID;
+
+@Entity
+@Table(name = "chapter")
+public class ChapterEntity {
+
+    @Id
+    @Column(name = "id", length = 200)
+    private String id;
+
+    @Column(name = "book_id", nullable = false)
+    private UUID bookId;
+
+    @Column(name = "number", nullable = false)
+    private int number;
+
+    @Column(name = "title", length = 500)
+    private String title;
+
+    @Column(name = "page_start")
+    private Integer pageStart;
+
+    @Column(name = "created_at", nullable = false)
+    private Instant createdAt;
+
+    public ChapterEntity() {}
+
+    public ChapterEntity(String id, UUID bookId, int number, String title, Integer pageStart) {
+        this.id = id;
+        this.bookId = bookId;
+        this.number = number;
+        this.title = title;
+        this.pageStart = pageStart;
+        this.createdAt = Instant.now();
+    }
+
+    public String getId() { return id; }
+    public UUID getBookId() { return bookId; }
+    public int getNumber() { return number; }
+    public String getTitle() { return title; }
+    public Integer getPageStart() { return pageStart; }
+    public Instant getCreatedAt() { return createdAt; }
+}