feat: add 6 more skins (PS1, PS3, Wii, NDS, Dreamcast, JV2002)

Brings the catalog to nine. Each is a single scoped [data-theme="..."]
CSS file plus a registry entry — no markup changes.

- ps1: charcoal BIOS, gray panels, uppercase letterspacing
- ps3: animated XMB sky gradient + drifting wave, black glass
- wii: white channels, rounded pills, soft blue glow
- nds: silver shell with content framed as the touch screen
- dreamcast: cream BIOS, conic-gradient orange swirl, lowercase blue
- jv2002: dense boxy portal, Verdana 11px, red masthead, blue nav tabs

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/admin/(panel)/layout.tsx

@@ -0,0 +1,38 @@
+import type { ReactNode } from "react";
+import Link from "next/link";
+import { requireAdmin } from "@/lib/auth";
+import { logoutAction } from "../actions";
+
+// Guarded chrome for every authenticated admin page. Login lives outside this
+// group so it never inherits the nav or the auth gate.
+export default async function PanelLayout({
+  children,
+}: {
+  children: ReactNode;
+}) {
+  await requireAdmin();
+
+  return (
+    <div className="rb-admin-shell">
+      <header className="rb-admin-bar">
+        <Link href="/admin" className="rb-admin-brand">
+          RetroBlog Admin
+        </Link>
+        <nav className="rb-admin-nav">
+          <Link href="/admin">Dashboard</Link>
+          <Link href="/admin/posts">Posts</Link>
+          <Link href="/admin/settings">Settings</Link>
+          <Link href="/" target="_blank">
+            View site ↗
+          </Link>
+        </nav>
+        <form action={logoutAction} className="rb-admin-logout">
+          <button className="rb-btn rb-btn-ghost" type="submit">
+            Sign out
+          </button>
+        </form>
+      </header>
+      <main className="rb-admin-main">{children}</main>
+    </div>
+  );
+}