BERLIN — China was once the promised land for German industry. Now it's a massive strategic headache for Chancellor Friedrich Merz, who departs on his inaugural visit to Beijing on Tuesday. For years, Berlin was the driving force behind closer EU relations with China — brushing aside human rights concerns to lobby for a landmark investment deal in 2020 . Closer trade relations with China, German leaders argued, would have a moderating effect on the regime in Beijing, a justification