After being pummeled for weeks on Capitol Hill over the president’s budget, Food and Drug Commissioner Andrew C. von Eschenbach has written Congress that the agency needs an immediate infusion of $275 million to ensure that imported foods, drugs and medical devices are safe. The request offers a detailed spending plan for such things as opening new foreign offices, increasing inspections and constructing new databases to track drug hazards. Dr. von Eschenbach's action — a rare divergence from White House policy by a presidential appointee — surprised agency observers and was taken as perhaps a sign of the president's waning influence in the closing months of his presidency.