Checkout: Visual glitch on card flip for single checkout

[danimoh]

The card is cutoff on the top during the flip animation for single checkouts.

Single.Checkout.Card.Flip.Visual.Glitch.mp4

[sisou]

Checkout with other wallets has been disabled recently in 29023e8 for checkout version 1, as that version does not support the CSRF and callback parameters, and thus cannot detect external NIM payments.