A 28-year-old man with newly diagnosed HIV infection (CD4 count 45 cells/μL) presents to the emergency department with severe dysphagia, odynophagia, and retrosternal chest pain for 5 days. Oral examination reveals white plaques on the tongue and soft palate that do not scrape off easily. Endoscopy shows extensive white plaques and ulceration extending into the esophagus. Histopathology demonstrates fungal hyphae and pseudohyphae invading the esophageal mucosa. Which antifungal agent is contraindicated in this patient due to the risk of severe hepatotoxicity and drug interactions with antiretroviral therapy?