A 48-year-old woman with hepatitis B-related cirrhosis (Child-Pugh Class B) presents with abdominal distension and weight gain over 2 weeks. Examination reveals tense ascites. Serum albumin is 2.8 g/dL, total bilirubin 2.1 mg/dL, and INR 1.4. Ascitic fluid analysis shows SAAG 2.4 g/dL, protein 1.2 g/dL, and no spontaneous bacterial peritonitis. She is on spironolactone 100 mg daily but remains symptomatic. What is the most appropriate next step in management?