MATT SPETALNICK, HUMEYRA PAMUK and PATRICIA ZENGERLE U.S. President Joe Biden took office in January determined to focus his time and energy on the coronavirus pandemic and economic downturn at home and big challenges such as China, Russia and Iran abroad. But after a Gaza conflict that required intensive behind-the-scenes U.S. diplomacy, his aides are having to reorder their priorities as they seek to stabilize an Israel-Hamas ceasefire, craft a reconstruction aid plan for the Palestinians and prevent a recurrence of what became Biden's first foreign policy crisis. The focus, one U.S. official said, is on "what would come next,…