add initial demo app

src/components/ui/Button.tsx

@@ -0,0 +1,14 @@
+interface ButtonProps extends React.ButtonHTMLAttributes<HTMLButtonElement> {
+  children: React.ReactNode;
+}
+
+export function Button({ children, className = "", ...props }: ButtonProps) {
+  return (
+    <button
+      className={`w-full max-w-xs mx-auto block bg-[#7C65C1] text-white py-3 px-6 rounded-lg transition-colors disabled:opacity-50 disabled:cursor-not-allowed disabled:hover:bg-[#7C65C1] hover:bg-[#6952A3] ${className}`}
+      {...props}
+    >
+      {children}
+    </button>
+  );
+}