feat: 友链入口迁至站点区并支持左右页脚独立开关

修复左侧栏/页脚开关无法关闭的问题，改为专用设置接口可靠写入。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/pages/admin/AdminSettingsPage.tsx

@@ -299,6 +299,8 @@ export default function AdminSettingsPage() {
           aside_show_recent_comments: false,
           aside_show_friend_links: true,
           aside_widgets: loadedAsideWidgets,
+          nav_show_friend_links: true,
+          footer_show_friend_links: true,
           feed_list_style: 'title',
           permalink_enabled: false,
           permalink_ext: 'html',