The Swiss National Bank said on Thursday it is ready to intervene in foreign exchange markets if a rebound in demand for the safe-haven franc drives the currency higher. It came as the central bank left its main policy rate unchanged at 0%, in a move widely expected by markets, keeping borrowing costs well below those seen in other major economies. In a statement, Martin Schlegel, chairman of the SNB's Governing Board, said the outbreak of the Middle East conflict on Feb. 28 initially heaped