Focus the sprint on private donations.

README now states the cut is creator donation QRs, not merchant checkout. The plan is donation UI, then the First 10 contest, then DonationPot only if time remains. Mainnet Ready wallet and the three verified pool transactions are listed so the hub can see them on master.

DonationPot is documented as a separate public-total rail: the helper is the jar, a sweep returns funds to a shielded note, and Cairo does not belong on the private transfer path.