.... Avina's criminal conduct. "[T]he proceeds of an offense do not exist before the offense is committed, and when they come into existence, the government's interest under the relation-back doctrine immediately vests." United..., 567 (7th Cir. 1997) ("[O]nce the government wins a judgment of forfeiture, the relation-back doctrine provides that the right, title, and interest in the forfeited property vests in the United...