first implementation - image/drawing integration

backend/src/main/resources/db/migration/V4__document_hierarchy.sql

@@ -0,0 +1,28 @@
+-- ============================================================
+-- V4: Document hierarchy — chapter and section tables
+-- Supports parent-child retrieval pattern for RAG precision.
+-- ============================================================
+
+CREATE TABLE IF NOT EXISTS chapter (
+    id           VARCHAR(200) PRIMARY KEY,
+    book_id      UUID NOT NULL REFERENCES book(id) ON DELETE CASCADE,
+    number       INT NOT NULL DEFAULT 1,
+    title        VARCHAR(500),
+    page_start   INT,
+    created_at   TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE TABLE IF NOT EXISTS section (
+    id           VARCHAR(200) PRIMARY KEY,
+    chapter_id   VARCHAR(200) NOT NULL REFERENCES chapter(id) ON DELETE CASCADE,
+    book_id      UUID NOT NULL REFERENCES book(id) ON DELETE CASCADE,
+    number       VARCHAR(50),
+    title        VARCHAR(500),
+    page_start   INT NOT NULL,
+    page_end     INT NOT NULL,
+    full_text    TEXT NOT NULL,
+    created_at   TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_section_book    ON section(book_id);
+CREATE INDEX IF NOT EXISTS idx_section_chapter ON section(chapter_id);