Local residents have new job opportunities thanks to the array of new retail stores and restaurants that recently opened at Assembly Row. Somerville residents make up about 40 percent of the new hires working at the shopping center, according to new data released by retailers. The city and Federal Realty, the developer of Assembly Row, have held five job fairs since March 1, with two of the fairs created specifically to give Somerville residents the first chance to apply for jobs in the development. Assembly Row also offers an online job portal (www.assemblyrow.com/#work) to alert residents to new job openings as they are posted. As new commercial tenants sign leases in the complex, the developers promise to continue to help locals get jobs there..