fix(frontend): don't reload page on first service worker install

clientsClaim() fires controllerchange when the freshly installed service
worker takes control of the page on first visit, which reloaded the app
and wiped unsaved state such as login form input. Only reload after the
user explicitly confirmed an update.

Fixes #3251

frontend/src/components/home/UpdateNotification.vue

@@ -30,8 +30,11 @@ document.addEventListener('swUpdated', showRefreshUI, {once: true})
 
 navigator?.serviceWorker?.addEventListener(
 	'controllerchange', () => {
-		if (refreshing.value) return
-		refreshing.value = true
+		// clientsClaim() also fires this on first install — only reload after
+		// the user opted into an update, or unsaved state (e.g. login form
+		// input) gets wiped.
+		if (!refreshing.value) return
+		refreshing.value = false
 		window.location.reload()
 	},
 )
@@ -48,6 +51,7 @@ function refreshApp() {
 	if (!registration.value || !registration.value.waiting) {
 		return
 	}
+	refreshing.value = true
 	// Notify the service worker to actually do the update
 	registration.value.waiting.postMessage('skipWaiting')
 }