A 63-year-old man with long-standing type 2 diabetes and hypertension presents with gradually worsening bilateral leg swelling and frothy urine. Urinalysis shows 3+ protein, and ACR is 250 mg/mmol. eGFR is 55 mL/min/1.73 m². Blood pressure is 150/92 mmHg. What is the most appropriate first-line pharmacological intervention?