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/app/admin/content/ContentAdmin.tsx

@@ -42,7 +42,7 @@ import {
 } from "@/lib/api";
 import { canModerateAuthor } from "@/lib/roles";
 import { formatRelative } from "@/lib/format";
-import { postPath } from "@/lib/urlStyle";
+import { postPath, commentAnchor } from "@/lib/urlStyle";
 import { toast } from "@/lib/toast";
 import { realtime, RT_MODERATION_CHANGED } from "@/lib/realtime";
 import Avatar from "@/components/Avatar";
@@ -692,7 +692,7 @@ export default function ContentAdmin({
                     c.post_title
                   ) : (
                     <Link
-                      href={`${postPath(urlStyle, c.post_id)}#comment-${c.id}`}
+                      href={`${postPath(urlStyle, c.post_id)}${commentAnchor(c.floor, c.is_root, c.id)}`}
                       className="hover:underline"
                       style={{ color: "var(--accent)" }}
                     >