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)/posts/new/page.tsx

@@ -0,0 +1,15 @@
+import PostForm from "../PostForm";
+
+export default async function NewPostPage({
+  searchParams,
+}: {
+  searchParams: Promise<{ error?: string }>;
+}) {
+  const { error } = await searchParams;
+  return (
+    <div className="rb-admin-page">
+      <h1 className="rb-admin-h1">New post</h1>
+      <PostForm titleError={error === "title"} />
+    </div>
+  );
+}