Update Bookmarks page header to match other feed page headers

Removes sticky behavior, backdrop blur, and background from the
header. Uses the same plain header style with back arrow, icon,
and title as Treasures and other feed pages.

src/pages/BookmarksPage.tsx

@@ -7,7 +7,7 @@ import { useAppContext } from '@/hooks/useAppContext';
 import { useBookmarks } from '@/hooks/useBookmarks';
 import { useCurrentUser } from '@/hooks/useCurrentUser';
 import { LoginArea } from '@/components/auth/LoginArea';
-import { cn } from '@/lib/utils';
+
 
 export function BookmarksPage() {
   const { config } = useAppContext();
@@ -22,12 +22,12 @@ export function BookmarksPage() {
 
   return (
       <main className="">
-        {/* Sticky header */}
-        <div className={cn('sidebar:sticky sidebar:top-0', 'flex items-center gap-4 px-4 pt-4 pb-5 bg-background/80 backdrop-blur-md z-10')}>
-          <Link to="/" className="p-2 rounded-full hover:bg-secondary transition-colors sidebar:hidden">
+        {/* Page header */}
+        <div className="flex items-center gap-4 px-4 mt-4 mb-1">
+          <Link to="/" className="p-2 -ml-2 rounded-full hover:bg-secondary transition-colors sidebar:hidden">
             <ArrowLeft className="size-5" />
           </Link>
-          <div className="flex items-center gap-2">
+          <div className="flex items-center gap-2 flex-1 min-w-0">
             <Bookmark className="size-5" />
             <h1 className="text-xl font-bold">Bookmarks</h1>
           </div>