feat(ui): complete phase 4 Poyraz UI foundation

components/auth/submit-button.tsx

@@ -1,8 +1,7 @@
 "use client";
 
 import { useFormStatus } from "react-dom";
-import { Button } from "@/components/ui/button";
-import { Loader2 } from "lucide-react";
+import { Button } from "poyraz-ui/atoms";
 import React from "react";
 
 interface SubmitButtonProps extends React.ComponentProps<typeof Button> {
@@ -18,10 +17,9 @@ export function SubmitButton({
   const { pending } = useFormStatus();
 
   return (
-    <Button type={type} disabled={pending} {...props}>
+    <Button type={type} disabled={pending} loading={pending} aria-busy={pending} {...props}>
       {pending ? (
         <>
-          <Loader2 className="h-4 w-4 animate-spin" />
           {pendingText || children}
         </>
       ) : (