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/u/[id]/UserProfileContent.tsx

@@ -1,6 +1,6 @@
 import Link from "next/link";
 import {
-  FileText, MessageCircle, AlertCircle, Bookmark, UserPlus,
+  FileText, MessageCircle, AlertCircle, Bookmark, UserPlus, Pin, Star,
 } from "lucide-react";
 import Pagination from "@/components/Pagination";
 import PostRow from "@/components/PostRow";
@@ -12,7 +12,7 @@ import { formatRelative } from "@/lib/format";
 import type {
   UserProfile, UserCommentsResponse, UserFavoritesResponse, UserFollowingResponse, PostListItem,
 } from "@/lib/api";
-import { postPath, userPath } from "@/lib/urlStyle";
+import { postPath, userPath, commentAnchor } from "@/lib/urlStyle";
 import { getPublicSettingsCached } from "@/lib/serverData";
 
 /** 本页卡片统一阴影；用 color-mix 让暗色主题自动加深，避免写死浅色阴影 */
@@ -44,10 +44,11 @@ async function PostCardItem({ post, allowComments }: { post: PostListItem; allow
       <div className="flex items-start gap-2">
         {pinned && (
           <span
-            className="mt-0.5 inline-flex shrink-0 items-center rounded px-1.5 py-px text-[11px] font-semibold leading-[1.5] text-white"
-            style={{ background: "#f59e0b" }}
+            className="badge-pin shrink-0 mt-0.5"
+            title="置顶"
+            aria-label="置顶"
           >
-            置顶
+            <Pin size={12} fill="currentColor" strokeWidth={2.2} aria-hidden />
           </span>
         )}
         <h2
@@ -56,7 +57,11 @@ async function PostCardItem({ post, allowComments }: { post: PostListItem; allow
         >
           {post.title}
         </h2>
-        {post.recommended && <span className="badge-rec shrink-0">推荐</span>}
+        {post.recommended && (
+          <span className="badge-rec shrink-0 mt-0.5" title="推荐" aria-label="推荐">
+            <Star size={12} fill="currentColor" strokeWidth={2.2} aria-hidden />
+          </span>
+        )}
       </div>
       <div
         className="mt-2 flex flex-wrap items-center gap-x-3 gap-y-1.5 text-[12px]"
@@ -313,7 +318,7 @@ export default async function UserProfileContent({
             {(commentData.comments ?? []).map((c) => (
               <Link
                 key={c.id}
-                href={`${postPath(urlStyle, c.post_id)}#comment-${c.id}`}
+                href={`${postPath(urlStyle, c.post_id)}${commentAnchor(c.floor, c.is_root, c.id)}`}
                 className="group block px-4 sm:px-5 py-4 border-t transition-colors hover:bg-[var(--item-hover-bg)] focus-visible:bg-[var(--item-hover-bg)]"
                 style={{ borderColor: "var(--line)" }}
               >

frontend/app/u/[id]/page.tsx

@@ -258,9 +258,9 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
           />
         </div>
 
-        {/* 本人操作按钮 / 访客私聊：绝对定位在卡片右上角 */}
+        {/* 本人操作按钮 / 访客私聊：移动端独占顶部一行（避免遮挡徽章/签名），sm 起绝对定位右上角 */}
         {isOwner ? (
-          <div className="absolute top-3 right-3 z-20 flex items-center gap-2">
+          <div className="relative z-20 flex items-center justify-end gap-2 px-5 sm:px-6 pt-3 sm:absolute sm:top-3 sm:right-3 sm:px-0 sm:pt-0">
             <Link href={`${userPath(urlStyle, Number(id))}?tab=settings`} className="btn btn-line btn-sm">
               <PenLine size={13.5} />
               <span className="hidden sm:inline">编辑资料</span>
@@ -276,7 +276,7 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
             </Link>
           </div>
         ) : currentUser ? (
-          <div className="absolute top-3 right-3 z-20 flex items-center gap-2">
+          <div className="relative z-20 flex items-center justify-end gap-2 px-5 sm:px-6 pt-3 sm:absolute sm:top-3 sm:right-3 sm:px-0 sm:pt-0">
             <FollowButton userId={u.id} following={u.is_following === true} />
             <StaffUserMenu
               target={{
@@ -295,10 +295,10 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
           </div>
         ) : null}
 
-        {/* 身份 + 行内统计：垂直居中，高度约 120px */}
+        {/* 身份 + 行内统计：垂直居中，高度约 120px；移动端按钮已独占一行，无需右侧预留 */}
         <div
           className={`relative z-10 flex min-h-[120px] items-center gap-3.5 px-5 sm:px-6 py-3.5 ${
-            hasHeroActions ? "pr-24 sm:pr-32" : ""
+            hasHeroActions ? "sm:pr-32" : ""
           }`}
         >
           <ProfileHeroAvatar
@@ -374,7 +374,7 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
             </p>
             {u.signature && (
               <p
-                className="mt-1 text-[13px] leading-snug line-clamp-1"
+                className="mt-1 text-[13px] leading-snug whitespace-pre-wrap break-words"
                 style={{ color: "var(--ink-2)" }}
               >
                 {u.signature}