Restructure: move Vite project into app/, deploy build output to repo root

The webserver serves the repo checkout directly as static files, so
index.html at the repo root must be the production build (pointing at
hashed /assets/*.js) rather than the dev template (/src/main.tsx),
which was being served with an unrecognized application/octet-stream
MIME type and blocked by the browser.

- Move src/, public/, scripts/, server/, package.json, vite.config.ts,
  tsconfig.json, .env(.example), and the dev index.html into app/.
- Add app/scripts/deploy.mjs: copies app/dist/* into the repo root
  after every `vite build`, cleaning up stale hashed filenames.
- Wire it into `npm run build` (app/package.json).
- Update run.sh to operate from app/, and .gitignore for the new layout.
- Commit the current build output (index.html, assets/, manifest,
  sw.js, workbox-*.js, favicon.svg, icons/, LICENSE) to the repo root.
- Update README with the new project layout and deployment model.

app/src/components/Toast.tsx

@@ -0,0 +1,20 @@
+import { useEffect } from "react";
+import { useStore } from "../state/store";
+
+export function Toast() {
+  const toast = useStore((s) => s.toast);
+  const setToast = useStore((s) => s.setToast);
+
+  useEffect(() => {
+    if (!toast) return;
+    const t = setTimeout(() => setToast(null), 5000);
+    return () => clearTimeout(t);
+  }, [toast, setToast]);
+
+  if (!toast) return null;
+  return (
+    <div className="toast" onClick={() => setToast(null)}>
+      {toast}
+    </div>
+  );
+}