fix(ui): harden theme toggle accessibility

src/App.tsx

@@ -93,7 +93,7 @@ export default function App() {
   const [theme, setTheme] = useState<UiTheme>(() => {
     if (typeof window === "undefined") return "dark";
 
-    return resolveInitialUiTheme(window.localStorage);
+    return resolveInitialUiTheme(getThemeStorage());
   });
 
   useEffect(() => {
@@ -113,7 +113,7 @@ export default function App() {
 
   useEffect(() => {
     document.documentElement.dataset.uiTheme = theme;
-    persistUiTheme(theme, window.localStorage);
+    persistUiTheme(theme, getThemeStorage());
   }, [theme]);
 
   useEffect(() => {
@@ -173,3 +173,11 @@ function stateIcon(state: DashboardRuntimeState["state"]): string {
   if (state === "loading") return "mdi:progress-clock";
   return "mdi:tray";
 }
+
+function getThemeStorage(): Storage | undefined {
+  try {
+    return window.localStorage;
+  } catch {
+    return undefined;
+  }
+}