HONG KONG — Japan has been feeling the sting of China’s economic retaliation as their diplomatic spat over Taiwan worsens, with travel agencies canceling group tours and fears mounting over an outright ban on Japanese seafood and movies. China hinted that it might halt seafood imports from Japan on Wednesday after warning its citizens to avoid traveling there and postponing the release in China of at least two Japanese movies. The two largest economies in Asia have been locked in a war of words