A 54-year-old male with a 6-year history of HBV-related cirrhosis presents with abdominal distension and bilateral lower extremity edema for 1 month, worsening with oliguria for 2 days. Physical exam shows frog belly, positive fluid wave thrill, and pitting edema in both lower extremities. Laboratory tests reveal serum sodium 122 mmol/L and BUN 19 mmol/L. What is the most likely diagnosis?