SAN FRANCISCO (AP) — Netflix’s subscriber growth is bogging down even before the leading video streaming service confronts high-powered threats from Apple and Walt Disney Co. The latest sign of the challenges the company is facing emerged Wednesday with the release of its third-quarter results. The numbers provided further evidence that Netflix’s salad days may be over, particularly in the U.S., where most households that want its 12-year-old streaming service already have it. Netflix added 6.8 million subscribers worldwide from July through September, below the 7 million customers forecast by the Los Gatos, California, company.