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/siteUrl.test.ts

@@ -6,7 +6,6 @@ import {
   canonicalPath,
   homeCanonicalQuery,
   isTrackingParam,
-  isWideShellPath,
   parseSiteOrigin,
   resolveSiteOrigin,
 } from "./siteUrl.ts";
@@ -117,23 +116,3 @@ describe("homeCanonicalQuery", () => {
   });
 });
 
-describe("isWideShellPath（书库页放宽档位）", () => {
-  it("覆盖三种伪静态风格的书库路径", () => {
-    assert.equal(isWideShellPath("/library"), true);
-    assert.equal(isWideShellPath("/library/abc"), true);
-    assert.equal(isWideShellPath("/library/abc/read"), true);
-    assert.equal(isWideShellPath("/library.html"), true);
-    assert.equal(isWideShellPath("/library-abc.html"), true);
-    assert.equal(isWideShellPath("/library-abc.html?sec=2"), true);
-    assert.equal(isWideShellPath("/library-abc-read-2.html"), true);
-  });
-  it("非书库路径不放宽", () => {
-    assert.equal(isWideShellPath("/"), false);
-    assert.equal(isWideShellPath("/post-1.html"), false);
-    assert.equal(isWideShellPath("/p-about.html"), false);
-    assert.equal(isWideShellPath("/u/5"), false);
-    assert.equal(isWideShellPath("/admin/library"), false);
-    assert.equal(isWideShellPath("/my-library.html"), false);
-    assert.equal(isWideShellPath(null), false);
-  });
-});