Via, one of the region’s largest independent ad agencies, recently moved its Boston-area operations to new digs in the city’s South End neighborhood. Celebrating at a party thrown by the shop were dozens of staffers and clients including Laurie McLachlan, vice president of marketing at investment house Brown & Co., Greg Smith, the Portland, Maine-based agency’s executive creative director and Leslie Kaplan, a Via principal. Via won the Brown & Co. business late last year; its first image ads for the client are in development.