Flyer edits save from the unsaved changes card

Discard puts the saved flyer back, a failed save shows what went wrong with the retry still in place, and the card holds at Saving until the change has actually landed rather than flashing back to unsaved. Drawing the preview in the page means it looks the same in every browser. On the same tab, the standalone QR code shows the color you picked and stays independent of the flyer’s own QR, so changing one no longer changes the other, and the QR section moved to the bottom of the page.