Fix cart clearing on success page

Use empty dependency array to ensure clear() runs once on mount.
Add logging and also clear isCheckingOut flag.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/components/ClearCartOnMount.tsx

@@ -5,8 +5,15 @@ import { useCart } from '@/lib/cartStore';
 
 export default function ClearCartOnMount() {
   const clear = useCart((s) => s.clear);
+
   useEffect(() => {
+    console.log('🧹 ClearCartOnMount: Clearing cart on success page');
     clear();
-  }, [clear]);
+    // Also clear the isCheckingOut flag if it was set
+    if (typeof window !== 'undefined') {
+      sessionStorage.removeItem('isCheckingOut');
+    }
+  }, []); // Empty dependency array - run once on mount
+
   return null;
 }