feat: 书库导入导出/图片变体/书籍搜索/小组件运行时等

新增：
- 书库导入导出（library_import/library_export）及测试
- 图片变体生成（image_variants）与响应式图片（responsiveImage）
- 书籍搜索（bookSearch）+ BookSearch/LibrarySearchGrid 组件
- 小组件运行时（widgetRuntime）与静态检查（widgetLint）
- 上传缓存中间件（upload_cache）与字体 CSS 提取脚本

其它：
- 后端 handlers/services 全量调整
- 前端页面、组件、库函数与配置更新

frontend/lib/bookSearch.test.ts

@@ -0,0 +1,92 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { markdownToSearchText, searchBook, type BookChapterIndex } from "./bookSearch.ts";
+
+describe("markdownToSearchText", () => {
+  it("条目卡指令保留值、剥离标记符号", () => {
+    const md = `[entries]
+## 安全气囊
+@tags 汽车 | 安全 | 主:被动
+@summary 气囊需配合安全带使用。
+备注 :: 详见召回公告
+@source NHTSA 报告 | https://a.gov/x
+[/entries]`;
+    const text = markdownToSearchText(md);
+    assert.ok(text.includes("安全气囊"));
+    assert.ok(text.includes("汽车"));
+    assert.ok(text.includes("主:被动"));
+    assert.ok(text.includes("气囊需配合安全带使用。"));
+    assert.ok(text.includes("备注 详见召回公告"));
+    assert.ok(text.includes("NHTSA 报告"));
+    assert.ok(!text.includes("@tags"));
+    assert.ok(!text.includes("@summary"));
+    assert.ok(!text.includes("@source"));
+    assert.ok(!text.includes("::"));
+    assert.ok(!text.includes("[entries"));
+    assert.ok(!text.includes("https://a.gov/x"));
+  });
+
+  it("锁定的 hide 块整体不可搜，未锁块保留正文", () => {
+    const md = `公开段落内容。
+
+[hide login]
+登录后可见的秘密
+[/hide]
+
+[hide points=10 locked]
+积分秘密内容
+[/hide]`;
+    const text = markdownToSearchText(md);
+    assert.ok(text.includes("公开段落内容"));
+    assert.ok(text.includes("登录后可见的秘密"));
+    assert.ok(!text.includes("积分秘密内容"));
+  });
+
+  it("剥离代码围栏与行内 markdown 语法但保留代码与锚文本", () => {
+    const md = "见 [官网说明](https://x.com) 与 `const x = 1`，\n\n```ts\ncodeInside();\n```";
+    const text = markdownToSearchText(md);
+    assert.ok(text.includes("官网说明"));
+    assert.ok(!text.includes("https://x.com"));
+    assert.ok(text.includes("const x = 1"));
+    assert.ok(text.includes("codeInside();"));
+    assert.ok(!text.includes("```"));
+  });
+});
+
+describe("searchBook", () => {
+  const chapters: BookChapterIndex[] = [
+    { no: 1, title: "第一章", plain: "今天天气很好，适合出门散步。路边有一朵花。" },
+    { no: 2, title: "第二章", plain: "第二章没有关键词。" },
+    { no: 3, title: "第三章", plain: "再次提到天气，天气真的不错。" },
+  ];
+
+  it("按章聚合命中数与片段，大小写不敏感", () => {
+    const hits = searchBook(chapters, "天气");
+    assert.equal(hits.length, 2);
+    assert.deepEqual(
+      hits.map((h) => [h.no, h.count]),
+      [
+        [1, 1],
+        [3, 2],
+      ]
+    );
+    assert.equal(hits[1].snippets[0].match, "天气");
+    assert.ok(hits[1].snippets[0].after.includes("，天气真的"));
+  });
+
+  it("片段最多生成 SNIPPET_LIMIT 个，但 count 为真实总数", () => {
+    const cs: BookChapterIndex[] = [{ no: 1, title: "t", plain: "天气 天气 天气 天气" }];
+    const hits = searchBook(cs, "天气");
+    assert.equal(hits[0].count, 4);
+    assert.equal(hits[0].snippets.length, 3);
+    assert.deepEqual(hits[0].snippets.map((s) => s.ordinal), [0, 1, 2]);
+  });
+
+  it("空关键词返回空", () => {
+    assert.deepEqual(searchBook(chapters, "  "), []);
+  });
+
+  it("无命中返回空数组", () => {
+    assert.deepEqual(searchBook(chapters, "航天飞机"), []);
+  });
+});