By Francesco Canepa and Jan Strupczewski FRANKFURT/BRUSSELS (Reuters) -The euro zone’s economy stagnated last year, weighed down by an industrial malaise in Germany, its former powerhouse, data showed on Tuesday. The 20 countries that share the euro barely avoided an outright recession in the final quarter of last year even as the zone’s biggest trading partner, the United States, chalked up impressively brisk growth. The euro zone’s underperformance was mostly due to weakness in Germany, which has seen its business model – predicated on cheap energy from Russia and intense two-way trade with …