ShipHero: Packing Note Picks Up Fulfillment Instructions

ShipHero's packing note was reading from a legacy handling-instructions field and missing the per-fulfillment instructions added with the new notes feature. The packing note now reads a fulfillment's instructions first, falling back to the order-level note when the fulfillment doesn't have its own — so what an operator types into a fulfillment's instructions actually reaches the ShipHero pickers.