One day last November, Luis Maldonado celebrated his 50th birthday with a cake and people he considered his family around the table. A pretty normal scene, except for the setting: the office of Guajira, the start-up that gave Maldonado a loan for an e-bike that has fueled his work as a delivery worker. Maldonado is one of the three million Venezuelans who have settled in neighboring Colombia as the crisis in their country deepens. Venezuela faces political unrest and an acute economic crisis, an...