fix(ui): change ui theme color

feat(calc): add geogebra based graph calculator for tests

src/components/ChoiceCard.tsx

@@ -16,7 +16,7 @@ export const ChoiceCard = ({
   <button
     onClick={onClick}
     className={`rounded-2xl border p-4 text-left transition flex flex-col
-      ${selected ? "border-purple-600 bg-purple-50" : "hover:border-gray-300"}`}
+      ${selected ? "border-indigo-600 bg-indigo-50" : "hover:border-gray-300"}`}
   >
     <div className="flex justify-between">
       <span className="font-satoshi-bold text-lg">{label}</span>