fix(03): IN-03 guard localStorage access in InstallPrompt

apps/pwa/src/components/InstallPrompt.tsx

@@ -278,10 +278,27 @@ function WalkthroughSheet({ onClose }: WalkthroughSheetProps) {
  *
  * Mount this at the top level of CalendarShell, below the nav bar.
  */
+// IN-03: localStorage access is guarded — in private-mode / SSR contexts the API can
+// throw on read or write. Mirrors calendarStore.ts's pattern so a storage failure
+// degrades gracefully (treated as "not dismissed") instead of crashing the component.
+function readDismissed(): boolean {
+  try {
+    return localStorage.getItem('installPromptDismissed') === '1'
+  } catch {
+    return false
+  }
+}
+
+function persistDismissed(): void {
+  try {
+    localStorage.setItem('installPromptDismissed', '1')
+  } catch {
+    // Ignore write failures (private mode / storage disabled)
+  }
+}
+
 export function InstallPrompt() {
-  const [dismissed, setDismissed] = useState<boolean>(
-    () => localStorage.getItem('installPromptDismissed') === '1',
-  )
+  const [dismissed, setDismissed] = useState<boolean>(readDismissed)
   const [walkthroughOpen, setWalkthroughOpen] = useState(false)
   const { canInstall, triggerInstall } = useAndroidInstallPrompt()
 
@@ -295,7 +312,7 @@ export function InstallPrompt() {
   if (installed) return null
 
   function dismiss() {
-    localStorage.setItem('installPromptDismissed', '1')
+    persistDismissed()
     setDismissed(true)
   }