Fix TOTP QR render

Update TotpEnrollmentWizard to handle QR code data_uri gracefully by using enrollmentData.qr_code directly if it already starts with data:, otherwise prefix with data:image/png;base64,. This prevents invalid HTML and extra requests.

X-Lovable-Edit-ID: edt-779080b3-442d-4aeb-aaaf-e0e3c26b795d

src/components/security/TotpEnrollmentWizard.tsx

@@ -205,7 +205,7 @@ export function TotpEnrollmentWizard({
             <>
               <div className="flex justify-center p-4 bg-white rounded-lg">
                 <img
-                  src={`data:image/png;base64,${enrollmentData.qr_code}`}
+                  src={enrollmentData.qr_code.startsWith('data:') ? enrollmentData.qr_code : `data:image/png;base64,${enrollmentData.qr_code}`}
                   alt="TOTP QR Code"
                   className="w-48 h-48"
                 />