Add the Sandbar mobile companion PWA

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/index.html

@@ -0,0 +1,18 @@
+<!doctype html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover">
+<meta name="theme-color" content="#1f5c5c">
+<meta name="color-scheme" content="light dark">
+<title>Sandbar</title>
+<link rel="manifest" href="manifest.webmanifest">
+<link rel="icon" href="icon.svg" type="image/svg+xml">
+<link rel="apple-touch-icon" href="icon-192.png">
+<link rel="stylesheet" href="app.css">
+</head>
+<body>
+<div id="app" aria-live="polite"></div>
+<script type="module" src="app.js"></script>
+</body>
+</html>