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/pages/PagesAdmin.tsx

@@ -4,7 +4,7 @@ import { useEffect, useMemo, useRef, useState } from "react";
 import Link from "next/link";
 import { useRouter, useSearchParams } from "next/navigation";
 import { Ellipsis, ExternalLink, FileText, Plus } from "lucide-react";
-import { apiAdminDeleteSitePage, type SitePage } from "@/lib/api";
+import { apiAdminDeleteSitePage, apiAdminPurgeSitePage, type SitePage } from "@/lib/api";
 import { formatDateTime, formatRelative } from "@/lib/format";
 import { sitePagePublicPath } from "@/lib/sitePagePath";
 import { useUrlStyle } from "@/components/SiteBrandProvider";
@@ -61,8 +61,14 @@ export default function PagesAdmin({
   const [menuUp, setMenuUp] = useState(false);
   const menuRef = useRef<HTMLDivElement>(null);
 
-  const publishedCount = useMemo(() => list.filter((p) => p.published).length, [list]);
-  const draftCount = useMemo(() => list.filter((p) => !p.published).length, [list]);
+  const publishedCount = useMemo(
+    () => list.filter((p) => p.published && !p.deleted).length,
+    [list]
+  );
+  const draftCount = useMemo(
+    () => list.filter((p) => !p.published && !p.deleted).length,
+    [list]
+  );
 
   const filtered = useMemo(() => {
     if (statusFilter === "published") return list.filter((p) => p.published);
@@ -93,9 +99,16 @@ export default function PagesAdmin({
   async function remove(p: SitePage) {
     setDeletingId(p.id);
     try {
-      await apiAdminDeleteSitePage(p.id);
-      setList((l) => l.filter((x) => x.id !== p.id));
-      toast("页面已删除", "ok");
+      if (p.deleted) {
+        // 已软删的页面：彻底删除（不可恢复，释放 slug）
+        await apiAdminPurgeSitePage(p.id);
+        setList((l) => l.filter((x) => x.id !== p.id));
+        toast("页面已彻底删除，地址可重新使用", "ok");
+      } else {
+        await apiAdminDeleteSitePage(p.id);
+        setList((l) => l.map((x) => (x.id === p.id ? { ...x, deleted: true } : x)));
+        toast("页面已删除，可在列表中彻底删除以释放地址", "ok");
+      }
     } catch (e) {
       toast(e instanceof Error ? e.message : "删除失败");
     } finally {
@@ -170,20 +183,30 @@ export default function PagesAdmin({
                   const updated = p.updated_at || "";
                   const path = sitePagePublicPath(p.slug, urlStyle);
                   return (
-                    <tr key={p.id}>
+                    <tr key={p.id} style={p.deleted ? { opacity: 0.65 } : undefined}>
                       <td data-label="页面">
-                        <Link href={editHref(p.id, statusFilter)} className="admin-doc-title" title={p.title}>
-                          {p.title}
-                        </Link>
+                        {p.deleted ? (
+                          <span className="admin-doc-title" title={p.title}>
+                            {p.title}
+                          </span>
+                        ) : (
+                          <Link href={editHref(p.id, statusFilter)} className="admin-doc-title" title={p.title}>
+                            {p.title}
+                          </Link>
+                        )}
                         <p className="admin-doc-path">
                           <code>{path}</code>
                         </p>
                         {p.excerpt ? <p className="admin-doc-excerpt">{p.excerpt}</p> : null}
                       </td>
                       <td data-label="状态">
-                        <AdminStatusChip tone={p.published ? "ok" : "warn"}>
-                          {p.published ? "已发布" : "草稿"}
-                        </AdminStatusChip>
+                        {p.deleted ? (
+                          <AdminStatusChip tone="danger">已删除</AdminStatusChip>
+                        ) : (
+                          <AdminStatusChip tone={p.published ? "ok" : "warn"}>
+                            {p.published ? "已发布" : "草稿"}
+                          </AdminStatusChip>
+                        )}
                       </td>
                       <td data-label="展示位置">{placeLabel(p)}</td>
                       <td data-label="排序" className="tabular-nums">
@@ -200,10 +223,12 @@ export default function PagesAdmin({
                       </td>
                       <td data-label="操作">
                         <div className="admin-doc-row-actions">
-                          <Link href={editHref(p.id, statusFilter)} className="admin-doc-textbtn">
-                            编辑
-                          </Link>
-                          {p.published ? (
+                          {!p.deleted ? (
+                            <Link href={editHref(p.id, statusFilter)} className="admin-doc-textbtn">
+                              编辑
+                            </Link>
+                          ) : null}
+                          {p.published && !p.deleted ? (
                             <a
                               href={path}
                               target="_blank"
@@ -248,7 +273,7 @@ export default function PagesAdmin({
                                     setDeleteTarget(p);
                                   }}
                                 >
-                                  删除
+                                  {p.deleted ? "彻底删除" : "删除"}
                                 </button>
                               </div>
                             ) : null}
@@ -277,15 +302,17 @@ export default function PagesAdmin({
 
       <ConfirmDialog
         open={!!deleteTarget}
-        title="删除单页"
+        title={deleteTarget?.deleted ? "彻底删除单页" : "删除单页"}
         message={
           deleteTarget
-            ? `确定删除「${deleteTarget.title}」吗？当前为${deleteTarget.published ? "已发布" : "草稿"}。删除后前台不再显示，后台也不能恢复。`
+            ? deleteTarget.deleted
+              ? `确定彻底删除「${deleteTarget.title}」吗？删除后不可恢复，地址将释放可重新使用。`
+              : `确定删除「${deleteTarget.title}」吗？当前为${deleteTarget.published ? "已发布" : "草稿"}。删除后前台不再显示，可在列表中彻底删除以释放地址。`
             : ""
         }
         danger
         busy={deletingId != null}
-        confirmLabel="删除"
+        confirmLabel={deleteTarget?.deleted ? "彻底删除" : "删除"}
         onCancel={() => deletingId == null && setDeleteTarget(null)}
         onConfirm={() => {
           if (deleteTarget) void remove(deleteTarget);