By Lucy Raitano LONDON (Reuters) – Mining and oil firms led an 11% jump in dividend payouts to a first-quarter record of $302.5 billion, according to a closely-watched global report, though it warned companies face a growing number of challenges in the months ahead. The war in Ukraine, geopolitical tensions, high energy and commodity prices, rapid inflation and rising interest rates are all likely to impact companies’ dividend prospects, according to British asset management group Janus Henderson. “These challenges also mean greater uncertainty that is likely to affect corporate decision makin…