Add fullscreen PWA support

web/src/pwa.ts

@@ -0,0 +1,9 @@
+export function registerServiceWorker() {
+  if (!import.meta.env.PROD || !("serviceWorker" in navigator)) return;
+
+  window.addEventListener("load", () => {
+    void navigator.serviceWorker.register("/sw.js").catch((error: unknown) => {
+      console.warn("Sybil service worker registration failed", error);
+    });
+  });
+}