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/post/[id]/page.tsx

@@ -8,6 +8,8 @@ import {
   MessageCircle,
   Flame,
   ChevronRight,
+  Pin,
+  Star,
 } from "lucide-react";
 import {
   fetchPostDetail,
@@ -358,22 +360,31 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
     absoluteCanonical(postPath(urlStyle, post.id), commentPage > 1 ? { page: commentPage } : undefined) ||
     entityUrl;
   const authorName = post.user.nickname || post.user.username;
+  // 楼层号 = 跨页连续的主评论序号（含被过滤掉的软删/空占位），故按未过滤索引计算
   const visibleFloors: JsonLdVisibleComment[] = canFetchComments
     ? comments
-        .filter((c) => !c.deleted && (c.content || "").trim())
-        .map((c) => ({
-          id: c.id,
-          content: c.content,
-          created_at: c.created_at,
-          author: c.user
-            ? { id: c.user.id, name: c.user.nickname || c.user.username }
-            : undefined,
-        }))
+        .map((c, i): JsonLdVisibleComment | null =>
+          !c.deleted && (c.content || "").trim()
+            ? {
+                id: c.id,
+                floor: (commentPage - 1) * 20 + i + 1,
+                is_root: true,
+                content: c.content,
+                created_at: c.created_at,
+                author: c.user
+                  ? { id: c.user.id, name: c.user.nickname || c.user.username }
+                  : undefined,
+              }
+            : null
+        )
+        .filter((x): x is JsonLdVisibleComment => x !== null)
     : [];
   const acceptedForLd: JsonLdVisibleComment | null =
     canFetchComments && acceptedAnswer && !acceptedAnswer.deleted && acceptedAnswer.content?.trim()
       ? {
           id: acceptedAnswer.id,
+          floor: acceptedAnswer.floor,
+          is_root: acceptedAnswer.is_root,
           content: acceptedAnswer.content,
           created_at: acceptedAnswer.created_at,
           author: acceptedAnswer.user
@@ -475,15 +486,27 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
             <div className="panel p-4 sm:p-6 lg:p-8 max-sm:-mx-4 max-sm:rounded-none max-sm:border-x-0 max-sm:shadow-none">
                 <header className="mb-5 sm:mb-7">
                 <div className="flex items-start gap-2 flex-wrap mb-6">
-                  {/* 仅置顶/推荐在标题左侧 */}
-                  {post.pinned > 0 && <span className="badge-pin shrink-0 mt-2 sm:mt-3">置顶</span>}
-                  {post.recommended && <span className="badge-rec shrink-0 mt-2 sm:mt-3">推荐</span>}
-                  <h1
-                    className="text-[26px] sm:text-[34px] font-extrabold leading-tight tracking-tight min-w-0"
-                    style={{ color: "var(--ink)" }}
-                  >
-                    {post.title}
-                  </h1>
+                  {/* 置顶/推荐与标题包在同一不可折行的 flex item 内：外层 flex-wrap 收集行时只看
+                      已在行内元素的收缩能力，shrink-0 徽章会让超长 h1 整体掉到第二行；内层 min-w-0
+                      使 h1 在徽章旁的剩余空间内折行，徽章始终与标题首行同行（移动端） */}
+                  <div className="flex items-start gap-2 min-w-0">
+                    {post.pinned > 0 && (
+                      <span className="badge-pin shrink-0 mt-2 sm:mt-3" title="置顶" aria-label="置顶">
+                        <Pin size={13} fill="currentColor" strokeWidth={2.2} aria-hidden />
+                      </span>
+                    )}
+                    {post.recommended && (
+                      <span className="badge-rec shrink-0 mt-2 sm:mt-3" title="推荐" aria-label="推荐">
+                        <Star size={13} fill="currentColor" strokeWidth={2.2} aria-hidden />
+                      </span>
+                    )}
+                    <h1
+                      className="text-[26px] sm:text-[34px] font-extrabold leading-tight tracking-tight min-w-0"
+                      style={{ color: "var(--ink)" }}
+                    >
+                      {post.title}
+                    </h1>
+                  </div>
                   {/* 其余徽章紧跟标题右侧；问答不显示类型徽章 */}
                   {postType !== "discussion" && postType !== "question" && (
                     <span className="badge-type shrink-0 mt-2 sm:mt-3">{postTypeLabel(postType)}</span>