A 57-year-old man presents to the urgent care clinic complaining of recurrent, dull epigastric discomfort that has been worsening over the past several months, now becoming more persistent. He notes that the pain is occasionally exacerbated after fatty meals but is not relieved by antacids. His past medical history is significant for long-standing obesity, controlled hypertension, type 2 diabetes, and a history of chronic heavy alcohol consumption. Current medications include insulin, metformin, and lisinopril. On examination, he is afebrile with a temperature of 37.0°C, blood pressure of 145/88 mmHg, pulse of 82/min, and respirations of 16/min. His oxygen saturation is 99% on room air. Abdominal palpation reveals mild tenderness in the epigastrium and right upper quadrant, without rebound or guarding. No jaundice or palpable masses are noted. Initial laboratory studies and an abdominal radiograph were performed, the latter revealing a distinct curvilinear calcification in the right upper quadrant, consistent with a porcelain gallbladder. Considering the radiographic findings and clinical presentation, what is the most likely diagnosis and the critical next step in management?