OAKLAND, Calif. — Shipping lines and the dockworkers union said yesterday that talks on a new contract have broken down, raising the possibility of labor disruptions at West Coast ports later this week. Each side gave different reasons for the impasse, but its effect is clear — as of last night, there will be no contract covering the dockworkers who handle the booming Pacific Rim trade at 29 major West Coast ports. The break means that the 10,500 members of the International Longshore and Warehouse Union can stage work slowdowns. If they do, the shipping lines that employ them say...