Kink.com has seen plenty of belt-tightening over the years, with people tied to objects like chairs in the name of bondage. But in recent years, the straps have become snugger financially, too, as free pornography dug into its business. Now, the bondage video company — part of San Francisco’s tech and sex scene — is undergoing a transformation, with a new CEO, a different headquarters and a shift from porn video production to content distribution and e-commerce.