The biggest blackout in Venezuela’s history stretched to about 22 hours Friday, as dialysis patients went without treatment, airlines canceled flights and factories and schools shut their doors in a nation reeling from an economic collapse. Electricity went out Thursday afternoon, plunging some 30 million people into darkness in a country mired in political turmoil and hyperinflation. Power was restored in much of the capital on Friday afternoon but the rest of the country’s status was unclear. …