Switch Pay round-1 mockups

Open a card for the live HTML. Screens 3 to 5 came from Stitch; 1 and 2 are hand-built with the same tokens. Notes at the bottom.

1. Marketing homedesktop, mobile screenshot: 01-home-mobile.png

2. Pricing + calculatordesktop, live JS calculator

3. Hosted checkoutmobile, app tiles + summary

4. Venmo payment pagemobile. Note: the green button is being replaced by the live tracker

5. Merchant applicationdesktop

Home, phone widthscreenshot

design-notes.md (palette, type, component recipes, headline options)