fix(ui): add timeout to service-worker readiness in push subscription flows

Wraps navigator.serviceWorker.ready with a 10s timeout so subscribe,
unsubscribe, and existing-subscription checks surface a recoverable
error instead of hanging indefinitely when SW registration fails.

ui/src/ui/push-subscription.ts

@@ -30,6 +30,22 @@ export function detectWebPushState(): WebPushState {
   };
 }
 
+/** Timeout (ms) for service-worker readiness. */
+const SW_READY_TIMEOUT = 10_000;
+
+/**
+ * Await service-worker readiness with a timeout so callers don't hang
+ * indefinitely when registration fails or sw.js is unreachable.
+ */
+function swReady(): Promise<ServiceWorkerRegistration> {
+  return Promise.race([
+    navigator.serviceWorker.ready,
+    new Promise<never>((_, reject) =>
+      setTimeout(() => reject(new Error("Service worker not ready (timed out)")), SW_READY_TIMEOUT),
+    ),
+  ]);
+}
+
 /**
  * URL-safe base64 string to Uint8Array (for applicationServerKey).
  */
@@ -51,7 +67,7 @@ export async function getExistingSubscription(): Promise<PushSubscription | null
   if (!("serviceWorker" in navigator)) {
     return null;
   }
-  const registration = await navigator.serviceWorker.ready;
+  const registration = await swReady();
   return await registration.pushManager.getSubscription();
 }
 
@@ -78,7 +94,7 @@ export async function subscribeToWebPush(
   }
 
   // Subscribe via PushManager.
-  const registration = await navigator.serviceWorker.ready;
+  const registration = await swReady();
   const pushSubscription = await registration.pushManager.subscribe({
     userVisibleOnly: true,
     applicationServerKey: urlBase64ToUint8Array(vapidPublicKey).buffer as ArrayBuffer,
@@ -105,7 +121,7 @@ export async function subscribeToWebPush(
  * Unsubscribe from web push notifications.
  */
 export async function unsubscribeFromWebPush(client: GatewayBrowserClient): Promise<void> {
-  const registration = await navigator.serviceWorker.ready;
+  const registration = await swReady();
   const subscription = await registration.pushManager.getSubscription();
 
   if (subscription) {