A 62-year-old woman with long-standing hypertension and diabetes has persistent albuminuria with urine albumin-creatinine ratio (uACR) 40 mg/mmol and eGFR 52 mL/min/1.73 m². Her blood pressure is 148/88 mmHg on amlodipine alone. According to CKD management principles, which is the most appropriate next pharmacological step?