AT&T has announced that it will not have any iPhone 4 inventory to sell on a first-come, first-serve basis until June 29, five full days after the device’s official launch on June 24. Customers who pre-ordered the device from AT&T online should have their device delivered this week, while customers who pre-ordered for store delivery should receive a call letting them know when their iPhone 4 is ready for pickup. As of June 29, AT&T…