Ukraine has landed one of its most consequential blows yet against Russia's energy sector, knocking out the country's largest oil refinery just as Moscow is scrambling to contain a widening fuel crisis. Industry sources told Reuters that Gazprom Neft's Omsk refinery halted operations after a Ukrainian drone strike damaged key processing units at the 440,000-barrel-per-day facility. The refinery is Russia's largest gasoline producer, making the timing particularly painful for the Kremlin. According to the sources, the attack set fire to the CDU-10…