BEIJING/SHANGHAI (Reuters) – Activity in China’s factory sector shrank at its fastest rate in at least three years in August as domestic and export orders tumbled, increasing investors’ fears that the world’s second-largest economy may be lurching toward a hard landing. Hurt by soft demand, overcapacity and falling investment, the economy has also been buffeted by plunging shares and a shock yuan devaluation, in what some have called a “perfect storm” of factors that is rattling global markets and could strain relations with China’s major trading partners.