feat: 友链/书库/移动端导航/排行榜等多模块功能

新增模块：
- 友链（friendlink）后端处理 + 前端管理页与友链板
- 书库（library）：导入、章节、封面、阅读页、横竖版自适应 AdaptiveCoverSlot
- 顶栏导航（header_nav）配置与 MobileTabBar/MobileRailDrawers 移动端抽屉
- 排行榜 service 测试、站点页面测试、时间线发布（timeline_release）

其它改动：
- 后端 handlers/services 全量小幅调整
- 前端组件、库函数、URL/品牌/站点 URL 工具更新
- Lightbox 图片、MdEntries 条目卡、coverColor 派生色相等前端能力

frontend/components/MobileTabBar.tsx

@@ -2,26 +2,28 @@
 
 import Link from "next/link";
 import { usePathname } from "next/navigation";
-import { useEffect, useState } from "react";
+import { Fragment, useEffect, useState } from "react";
 import {
   Home,
-  Trophy,
+  BookOpen,
   PenSquare,
   MessageSquare,
   User as UserIcon,
 } from "lucide-react";
 import { apiChatUnreadSummary, type User } from "@/lib/api";
 import { useAllowMessages } from "@/components/MessagesPolicyProvider";
-import { useUrlStyle } from "@/components/SiteBrandProvider";
+import { useSiteBrand } from "@/components/SiteBrandProvider";
 import { onDocumentVisible } from "@/lib/visibilityReconcile";
-import { parseEntityPath, userPath, leaderboardPath } from "@/lib/urlStyle";
+import { userPath, libraryPath } from "@/lib/urlStyle";
 import { realtime, RT_CHAT_UNREAD } from "@/lib/realtime";
 import type { RtChatUnreadData } from "@/lib/realtime";
+import type { MobileTabKey } from "@/lib/mobileTabs";
 
 /**
  * 移动端全局底部公共菜单（lg 以下显示）：
- * 首页 / 排行榜 / 发帖 / 消息（未登录不显示）/ 我的。
- * 聊天页、发帖工作台、管理后台由 SiteChrome 控制不渲染，避免与锁视口布局冲突。
+ * 按 SiteBrand.mobile_tabs 配置顺序渲染（消息在未登录/未开放时不显示）。
+ * SiteChrome 只在启用 tab 的根路径渲染本组件，
+ * 避免与聊天 / 发帖工作台的锁视口布局冲突。
  */
 export default function MobileTabBar({
   user,
@@ -32,8 +34,8 @@ export default function MobileTabBar({
 }) {
   const pathname = usePathname();
   const allowMessages = useAllowMessages();
-  const urlStyle = useUrlStyle();
-  const lbHref = leaderboardPath(urlStyle);
+  const { url_style: urlStyle, mobile_tabs: mobileTabs } = useSiteBrand();
+  const libHref = libraryPath(urlStyle);
   const [chatUnread, setChatUnread] = useState(initialChatUnread);
 
   // 登录态经 router.refresh() 下发新 props 时校正徽标
@@ -80,8 +82,55 @@ export default function MobileTabBar({
   const isActive = (match: (p: string) => boolean) =>
     !!pathname && match(pathname);
 
+  // 配置已由 SiteBrandProvider normalize（白名单内子集，空回落全量）；数组顺序即展示顺序
+  const tabNodes: Record<MobileTabKey, React.ReactNode> = {
+    home: (
+      <TabLink
+        href="/"
+        icon={<Home size={20} />}
+        label="首页"
+        active={isActive((p) => p === "/")}
+      />
+    ),
+    library: (
+      <TabLink
+        href={libHref}
+        icon={<BookOpen size={20} />}
+        label="书库"
+        active={isActive((p) => p === libHref)}
+      />
+    ),
+    compose: (
+      <TabLink
+        href={user ? "/compose" : "/login"}
+        icon={<PenSquare size={18} />}
+        label="发帖"
+        prominent
+        active={false}
+      />
+    ),
+    messages: showMessages ? (
+      <TabLink
+        href="/chat"
+        icon={<MessageSquare size={20} />}
+        label="消息"
+        active={isActive((p) => p === "/chat")}
+        badge={chatUnread > 0 ? (chatUnread > 99 ? "99+" : chatUnread) : 0}
+      />
+    ) : null,
+    me: (
+      <TabLink
+        href={user ? userPath(urlStyle, user.id) : "/login"}
+        icon={<UserIcon size={20} />}
+        label="我的"
+        active={!!user && isActive((p) => p === userPath(urlStyle, user.id))}
+      />
+    ),
+  };
+
   return (
     <nav
+      data-j13-tabbar
       className="lg:hidden fixed bottom-0 inset-x-0 z-50 border-t"
       aria-label="底部导航"
       style={{
@@ -93,49 +142,9 @@ export default function MobileTabBar({
       }}
     >
       <div className="flex items-stretch">
-        <TabLink
-          href="/"
-          icon={<Home size={20} />}
-          label="首页"
-          active={isActive((p) => p === "/")}
-        />
-        <TabLink
-          href={lbHref}
-          icon={<Trophy size={20} />}
-          label="排行榜"
-          active={!!pathname && (pathname === lbHref || pathname.startsWith(`${lbHref}/`))}
-        />
-        <TabLink
-          href={user ? "/compose" : "/login"}
-          icon={<PenSquare size={18} />}
-          label="发帖"
-          prominent
-          active={false}
-        />
-        {showMessages && (
-          <TabLink
-            href="/chat"
-            icon={<MessageSquare size={20} />}
-            label="消息"
-            active={isActive((p) => p.startsWith("/chat"))}
-            badge={chatUnread > 0 ? (chatUnread > 99 ? "99+" : chatUnread) : 0}
-          />
+        {mobileTabs.map((key) =>
+          tabNodes[key] ? <Fragment key={key}>{tabNodes[key]}</Fragment> : null,
         )}
-        <TabLink
-          href={user ? userPath(urlStyle, user.id) : "/login"}
-          icon={<UserIcon size={20} />}
-          label="我的"
-          active={
-            !!user &&
-            isActive((p) => {
-              const parsed = parseEntityPath(p);
-              return (
-                (parsed?.kind === "user" && parsed.id === user.id) ||
-                p.startsWith(`${userPath(urlStyle, user.id)}/`)
-              );
-            })
-          }
-        />
       </div>
     </nav>
   );