Despite a still-tenuous economy that has hurt many of the nation’s ports, the big expansion bets the Port of Oakland made early this decade are now bearing fruit. Using money it raised from municipal bond sales, Oakland’s port since 2000 has invested about $1 billion to add storage yards and cargo-handling capacity and extend railroad lines. Today, the port handles about 2.2 million 20-foot containers of cargo compared with 1.5 million seven years ago and has grown to eight terminals from four during the same period. All that has helped Oakland’s port fare better than some rivals in the recession.