release: 发布 v0.5.1

新增能力：内置 4 套红头、3 套正式文档和 3 套标书主题，支持主题推荐页边距、页面装饰、页眉页脚和页码；增加结构化公文、项目报告及标书 Front Matter，内置 Fandol 中文字体、两份教程和 14 份主题示例。

桌面工作流：重组更多菜单，增加新建、保存、另存为快捷键和未保存确认；另存为后跟随新路径，主题示例自动切换主题，Desktop 发行包完整携带教程、示例与字体。

问题修复：修正红头标题居中与正式文档字体；围栏代码按正文宽度自动换行，长内容安全断行，至少两行即可在当前页分页，并统一保留 8px 左侧内容留白；Docker Web 镜像正确打包 samples。

兼容与部署：未声明主题推荐设置时继续使用 16mm 默认页边距；Web 隐藏不适用的另存为。正式镜像 yixiong/md-to-pdf:v0.5.1 内容 ID 为 sha256:72f519a69bfd6cb2f6df30c2be938e58ceb6f20e4748a32551874de3d436b276，Compose 健康运行。

验证结果：最终修复前 65 个测试文件、286 项测试通过，最终代码块与主题定向测试 27 项通过；全项目类型检查、生产构建和 git diff --check 通过。容器检出 14 套主题、17 份 Markdown，代码块回归 PDF 为 2 页且无越界。NSIS SHA-256 为 676CCE73D782B0B15AC6BC68F253CFBC4740383583E4DAA98F746EDF9999C5CC，ZIP SHA-256 为 82BF6ADF1200604F145CC86FA3ED193955CF6741EBEE3DF8953483515CFF621F。

apps/web/tests/export-settings.test.ts

@@ -2,7 +2,8 @@ import { describe, expect, it } from "vitest";
 import { defaultExportConfig } from "@md-to-pdf/core";
 import {
   EXPORT_CONFIG_STORAGE_KEY,
-  LEGACY_EXPORT_CONFIG_STORAGE_KEY,
+  LEGACY_EXPORT_CONFIG_V2_STORAGE_KEY,
+  LEGACY_EXPORT_CONFIG_V3_STORAGE_KEY,
   loadExportConfig,
   parseStoredExportConfig,
   saveExportConfig
@@ -10,14 +11,15 @@ import {
 
 function createMemoryStorage(
   initialValue: string | null = null,
-  legacyValue: string | null = null
+  legacyValue: string | null = null,
+  legacyKey = LEGACY_EXPORT_CONFIG_V3_STORAGE_KEY
 ) {
   const values = new Map<string, string>();
   if (initialValue) {
     values.set(EXPORT_CONFIG_STORAGE_KEY, initialValue);
   }
   if (legacyValue) {
-    values.set(LEGACY_EXPORT_CONFIG_STORAGE_KEY, legacyValue);
+    values.set(legacyKey, legacyValue);
   }
   return {
     getItem(key: string) {
@@ -52,26 +54,106 @@ describe("导出设置缓存", () => {
     ).toEqual(defaultExportConfig);
   });
 
-  it("将 v2 缓存迁移为 v3 并保留已有设置", () => {
+  it("将 v2 缓存迁移为 v4 并让默认页边距跟随主题", () => {
     const legacyConfig = {
       ...defaultExportConfig,
       version: 2,
       mermaid: undefined,
       paper: {
         ...defaultExportConfig.paper,
+        marginMode: undefined,
         format: "A5"
       }
     };
     const storage = createMemoryStorage(
       null,
-      JSON.stringify(legacyConfig)
+      JSON.stringify(legacyConfig),
+      LEGACY_EXPORT_CONFIG_V2_STORAGE_KEY
     );
 
     const migrated = loadExportConfig(storage);
-    expect(migrated.version).toBe(3);
+    expect(migrated.version).toBe(4);
     expect(migrated.paper.format).toBe("A5");
+    expect(migrated.paper.marginMode).toBe("theme");
     expect(migrated.mermaid).toEqual(defaultExportConfig.mermaid);
-    expect(storage.read()).toContain('"version":3');
+    expect(storage.read()).toContain('"version":4');
+  });
+
+  it("将改过页边距的 v3 缓存迁移为自定义模式", () => {
+    const legacyConfig = {
+      ...defaultExportConfig,
+      version: 3,
+      paper: {
+        ...defaultExportConfig.paper,
+        marginMode: undefined,
+        margins: {
+          top: "20mm",
+          right: "18mm",
+          bottom: "20mm",
+          left: "18mm"
+        }
+      }
+    };
+    const migrated = parseStoredExportConfig(
+      JSON.stringify(legacyConfig)
+    );
+
+    expect(migrated.version).toBe(4);
+    expect(migrated.paper.marginMode).toBe("custom");
+    expect(migrated.paper.margins).toEqual(legacyConfig.paper.margins);
+  });
+
+  it("将未改页眉页码的旧 v4 缓存迁移为跟随主题", () => {
+    const legacyConfig = {
+      ...defaultExportConfig,
+      pageDecorationsMode: undefined,
+      header: {
+        ...defaultExportConfig.header,
+        fontFamily: undefined
+      },
+      footer: {
+        ...defaultExportConfig.footer,
+        fontFamily: undefined,
+        showOnFirstPage: undefined
+      }
+    };
+    const migrated = parseStoredExportConfig(
+      JSON.stringify(legacyConfig)
+    );
+
+    expect(migrated.pageDecorationsMode).toBe("theme");
+    expect(migrated.header.fontFamily).toContain("Microsoft YaHei");
+    expect(migrated.footer.showOnFirstPage).toBe(true);
+  });
+
+  it("保留旧 v4 缓存中用户修改过的页眉页码", () => {
+    const legacyConfig = {
+      ...defaultExportConfig,
+      pageDecorationsMode: undefined,
+      header: {
+        ...defaultExportConfig.header,
+        enabled: true,
+        fontFamily: undefined,
+        center: {
+          enabled: true,
+          content: "${title}"
+        }
+      },
+      footer: {
+        ...defaultExportConfig.footer,
+        alignment: "right",
+        fontFamily: undefined,
+        showOnFirstPage: undefined
+      }
+    };
+    const migrated = parseStoredExportConfig(
+      JSON.stringify(legacyConfig)
+    );
+
+    expect(migrated.pageDecorationsMode).toBe("custom");
+    expect(migrated.header.enabled).toBe(true);
+    expect(migrated.header.center.content).toBe("${title}");
+    expect(migrated.footer.alignment).toBe("right");
   });
 
   it("保存并恢复经过校验的配置", () => {