How do I add a QR code to my email signature?

Export the card’s QR as a PNG. In Gmail or Outlook, open Signatures, insert the image, and hyperlink it to https://qr.zebeh.online/c/your-slug. Recipients click or scan and open the same live card. No app. Because the QR is dynamic, a job-title change does not require a new image if the file still points at the same URL. If you re-export a new PNG, replace the image in the signature.