SAN FRANCISCO — Attorney Martha Gomez has been waiting more than three years to hear from a federal court whether a group of farm workers in California’s Central Valley can proceed with their lawsuit alleging wage theft.The case in California’s Eastern District could result in payouts for thousands of migrant workers, but each passing day raises the possibility that they will have moved on and be impossible to track down, Gomez said.“Everybody is in limbo, and it’s hard to explain that,” …