MEXICO CITY — Mexico’s government on Monday signaled that it planned to hit back with trade restrictions of its own if President-elect Donald J. Trump followed through on his threats to impose sky-high tariffs on Mexican exports to the United States. “If you put 25 percents tariffs on me, I have to react with tariffs,” Marcelo Ebrard, Mexico’s economy minister, told a radio interviewer on Monday. “Structurally, we have the conditions to play in Mexico’s favor,” he added. “A tariff war doesn’t end well,” said Valeria Moy, the general director of the Mexican Institute for Competitiveness, an economic research institute....