feat: add PWA manifest and viewport configuration

app/layout.tsx

@@ -1,4 +1,4 @@
-import type { Metadata } from "next";
+import type { Metadata, Viewport } from "next";
 import { Geist, Geist_Mono } from "next/font/google";
 import "./globals.css";
 
@@ -17,6 +17,13 @@ export const metadata: Metadata = {
   description: "Daily music guessing game - Guess the song from short audio clips",
 };
 
+export const viewport: Viewport = {
+  themeColor: "#000000",
+  width: "device-width",
+  initialScale: 1,
+  maximumScale: 1,
+};
+
 export default function RootLayout({
   children,
 }: Readonly<{