A 52-year-old man with a 15-year history of alcohol use disorder presents to the emergency department with haematemesis and melaena. On examination, he is hypotensive (BP 85/50), tachycardic (HR 118/min), and has clinical signs of chronic liver disease including spider angiomas, palmar erythema, and ascites. Abdominal ultrasound shows cirrhotic liver morphology with portal vein diameter of 14 mm. Upper endoscopy reveals large oesophageal varices with active bleeding. After initial resuscitation and variceal ligation, the patient stabilizes. One week later, he develops acute kidney injury (creatinine rises from 1.2 to 3.8 mg/dL) with oliguria despite adequate fluid resuscitation. Urine sodium is <10 mEq/L and fractional excretion of sodium (FENa) is <0.1%. What is the most likely diagnosis?