Add Next.js web app

Feed with live updates and pinning, profiles with follow/pin, featured song
picker, settings for all music services, and account deletion.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MzFywujuH9TiuXbr9vjoX8

apps/web/src/app/layout.tsx

@@ -0,0 +1,19 @@
+import type { Metadata } from 'next';
+import { Nav } from '@/components/Nav';
+import './globals.css';
+
+export const metadata: Metadata = {
+  title: 'musicshare',
+  description: "See what your friends are listening to, and play it on your own service.",
+};
+
+export default function RootLayout({ children }: { children: React.ReactNode }) {
+  return (
+    <html lang="en">
+      <body>
+        <Nav />
+        <main className="container">{children}</main>
+      </body>
+    </html>
+  );
+}