Update ui/src/pages/Auth.tsx

Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

ui/src/pages/Auth.tsx

@@ -90,7 +90,7 @@ export function AuthPage() {
           <form
             className="mt-6 space-y-4"
             method="post"
-            action="/api/auth/sign-in/email"
+            action={mode === "sign_up" ? "/api/auth/sign-up/email" : "/api/auth/sign-in/email"}
             onSubmit={(event) => {
               event.preventDefault();
               if (mutation.isPending) return;