cake editor on mobile

The same editor markup and CSS as the desktop page, loaded at phone width so the real breakpoints from main.css apply: the design stacks above the editor, the product title is hidden, back / continue appear above and below the cake, and the price moves under the editor.

1. Edit textTwo message lines (100 characters each). The "Aa" button opens the font style menu: Lobster picked from the three fonts, colour chosen from the 15-colour palette, font size slider.
2. Edit imageAfter uploading a photo, "Position Photo" gives zoom, move and rotate. The photo shows through the round window in the cake.