A 48-year-old man from Mumbai presents with a 2-month history of recurrent painful oral ulcers and blistering of the palate and buccal mucosa. Over the past 4 weeks, flaccid blisters have appeared on the chest and abdomen, which rupture easily leaving erosions. He denies recent drug use or food allergies. Serum testing reveals positive indirect immunofluorescence with circulating autoantibodies against desmoglein 3 (anti-Dsg3). A skin biopsy from an erosion shows suprabasal acantholysis with preserved basal cell attachment to the basement membrane. What is the most appropriate initial treatment?