3e45e5b420
QR codes are used by `tailscale up --qr` to provide an easy way to open a web-page without transcribing a difficult URI. However, there’s no need for this feature if the client will never be called interactively. So this PR adds the `ts_omit_qrcodes` build tag. Updates #18182 Signed-off-by: Simon Law <sfllaw@tailscale.com>