frontend: rebuild bookmark page with drag-and-drop, search, and theme system

- bookmark management with dnd-kit reordering, bulk edit, search,
  category filter/rename, and meta auto-fetch
- migrate /bookmarks → /dashboard/bookmarks under (main) layout
- homepage redesign with category grid, /-key search, dock tooltips
- theme toggle + use-theme, sonner toasts, alert-dialog/skeleton,
  visual refresh of auth pages

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/app/(main)/layout.tsx

@@ -1,7 +1,5 @@
-import Link from "next/link";
 import { auth } from "@/auth";
-import { Button } from "@/components/ui/button";
-import { signOut } from "@/auth";
+import { HomeDock } from "../home-dock";
 
 export default async function MainLayout({
   children,
@@ -9,38 +7,15 @@ export default async function MainLayout({
   children: React.ReactNode;
 }) {
   const session = await auth();
-  const user = session?.user as any;
+  const user = session?.user as { role?: string } | undefined;
+  const isAdmin = user?.role === "admin";
 
   return (
-    <div className="min-h-screen bg-gray-50">
-      <header className="border-b bg-white">
-        <div className="mx-auto flex max-w-6xl items-center justify-between px-4 py-3">
-          <Link href="/" className="text-lg font-bold">
-            EvanPage
-          </Link>
-          <nav className="flex items-center gap-4">
-            <Link href="/dashboard" className="text-sm hover:underline">
-              仪表盘
-            </Link>
-            {user?.role === "admin" && (
-              <Link href="/bookmarks" className="text-sm hover:underline">
-                书签
-              </Link>
-            )}
-            <form
-              action={async () => {
-                "use server";
-                await signOut({ redirectTo: "/login" });
-              }}
-            >
-              <Button variant="ghost" size="sm" type="submit">
-                退出
-              </Button>
-            </form>
-          </nav>
-        </div>
-      </header>
-      <main className="mx-auto max-w-6xl px-4 py-6">{children}</main>
+    <div className="min-h-screen bg-gradient-to-br from-background via-background to-muted/40">
+      <main className="mx-auto max-w-6xl px-4 pt-8 pb-32 sm:px-6 sm:pt-12 lg:px-8">
+        {children}
+      </main>
+      <HomeDock isAuthenticated={!!session?.user} isAdmin={isAdmin} />
     </div>
   );
 }