A 45-year-old female presents with a 4-month history of a widespread rash and intense itching. Examination reveals a vesiculobullous eruption with annular, crusted, urticated plaques on the trunk and limbs. There is no mucosal involvement. Skin biopsy demonstrates eosinophilic spongiosis with no acantholysis. Direct immunofluorescence reveals epidermal intercellular IgG and C3. What is the most likely diagnosis?