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/app/admin/library/page.tsx

@@ -0,0 +1,36 @@
+import type { Metadata } from "next";
+import { Suspense } from "react";
+import { cookies } from "next/headers";
+import LibraryAdmin from "./LibraryAdmin";
+import { authCookieHeader } from "@/lib/cookies";
+import { fetchAdminLibraryDocs, type LibraryDoc } from "@/lib/api";
+import { getMeCached } from "@/lib/serverData";
+import { isAdminOrAbove } from "@/lib/roles";
+import Forbidden from "../Forbidden";
+
+export const metadata: Metadata = {
+  title: "书库管理",
+};
+
+export default async function AdminLibraryPage() {
+  const cookie = authCookieHeader(await cookies());
+  const me = await getMeCached(cookie || undefined);
+  if (!me.user || !isAdminOrAbove(me.user.role)) {
+    return <Forbidden text="书库管理仅管理员及以上角色可操作。" />;
+  }
+
+  let initial: LibraryDoc[] = [];
+  let initError = "";
+  try {
+    const res = await fetchAdminLibraryDocs(cookie || undefined);
+    initial = res.docs ?? [];
+  } catch (e) {
+    initError = e instanceof Error ? e.message : "加载书库失败";
+  }
+
+  return (
+    <Suspense fallback={<p className="meta px-1 py-6">加载书库列表…</p>}>
+      <LibraryAdmin initial={initial} initError={initError} />
+    </Suspense>
+  );
+}