A 58-year-old woman from Mumbai with a 5-year history of hypertension and type 2 diabetes mellitus presents with BP 164/102 mmHg. She is currently on metformin and lisinopril 10 mg daily. Serum creatinine is 1.4 mg/dL (eGFR 45 mL/min/1.73 m²), and urinalysis shows 1+ proteinuria. Her physician decides to intensify therapy. Which of the following would be the most appropriate addition to her current regimen?