Zastosowanie wszystkich poprawek UI i logiki kalkulatora

app/loading.tsx

@@ -0,0 +1,7 @@
+export default function Loading() {
+  return (
+    <div className="flex flex-col items-center justify-center min-h-screen bg-muted">
+      <div className="w-16 h-16 bg-primary rounded-full animate-pulse shadow-md"></div>
+    </div>
+  );
+}