fix: type assertion in useAppearance hook (#28)

Author: matthiasweiss

resources/js/hooks/use-appearance.tsx

@@ -36,7 +36,7 @@ export function useAppearance() {
     };
 
     useEffect(() => {
-        const savedAppearance = localStorage.getItem('appearance') as Appearance;
+        const savedAppearance = localStorage.getItem('appearance') as Appearance | null;
         updateAppearance(savedAppearance || 'system');
 
         return () => mediaQuery.removeEventListener('change', handleSystemThemeChange);