task-192: 迁移规范模板（docs/flyway-migration-template.md，六项必填头注释：目的/影响表数据量/锁表风险/验证SQL/回滚/窗口）+ 8 条测试

backend-java/src/test/java/com/nanri/aiimage/config/FlywayMigrationTemplateDocTest.java

@@ -0,0 +1,76 @@
+package com.nanri.aiimage.config;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * task-192：迁移规范模板契约。
+ * docs/flyway-migration-template.md 存在且六项必填（目的/影响表与数据量/锁表风险/验证 SQL/
+ * 回滚步骤/上线窗口）齐全，含示例 SQL，可被新迁移文件头注释引用。
+ */
+class FlywayMigrationTemplateDocTest {
+
+    private static final String DOC = "docs/flyway-migration-template.md";
+
+    private String doc() throws IOException {
+        return Files.readString(Path.of(System.getProperty("user.dir"), DOC));
+    }
+
+    @Test
+    void templateExists() throws IOException {
+        assertTrue(Files.exists(Path.of(System.getProperty("user.dir"), DOC)), "模板文件应存在");
+    }
+
+    @Test
+    void sixMandatoryFieldsPresent() throws IOException {
+        String text = doc();
+        for (int i = 1; i <= 6; i++) {
+            assertTrue(text.contains(i + ". "), "头注释应含第 " + i + " 项必填");
+        }
+    }
+
+    @Test
+    void fieldNamesListed() throws IOException {
+        String text = doc();
+        assertTrue(text.contains("变更目的"));
+        assertTrue(text.contains("影响表与数据量"));
+        assertTrue(text.contains("锁表风险"));
+        assertTrue(text.contains("验证 SQL"));
+        assertTrue(text.contains("回滚步骤"));
+        assertTrue(text.contains("上线窗口"));
+    }
+
+    @Test
+    void hasCopyableHeaderComment() throws IOException {
+        assertTrue(doc().contains("复制以下头注释"), "模板应提供可复制头注释");
+        assertTrue(doc().contains("V{N+1}__"), "头注释示例应含占位版本号");
+    }
+
+    @Test
+    void hasValidationSqlExample() throws IOException {
+        assertTrue(doc().contains("SELECT COUNT(*)"), "应含验证 SQL 示例");
+    }
+
+    @Test
+    void hasRollbackField() throws IOException {
+        assertTrue(doc().contains("回滚步骤"), "应含回滚步骤说明");
+    }
+
+    @Test
+    void hasUpgradeWindowField() throws IOException {
+        assertTrue(doc().contains("上线窗口"), "应含上线窗口说明");
+    }
+
+    @Test
+    void templateUsableByNewMigrations() throws IOException {
+        String text = doc();
+        assertTrue(text.contains("src/main/resources/db/"), "应说明迁移文件目录");
+        assertTrue(text.contains("只追加"), "应强调只追加不改历史");
+        assertTrue(text.contains("V109") || text.contains("最大现有版本"), "应说明版本号取最大现有版本+1");
+    }
+}