A 28-year-old woman presents to the outpatient clinic with a 3-week history of polyuria, polydipsia, and weight loss of 4 kg. She reports recent onset of fatigue and blurred vision. On examination, she appears lean (BMI 21 kg/m²). Laboratory investigations reveal: fasting blood glucose 280 mg/dL, HbA1c 9.2%, venous pH 7.28, serum bicarbonate 16 mEq/L, and positive serum ketones. C-peptide level is 0.3 ng/mL (normal 0.8–3.1). Anti-GAD and anti-IA2 antibodies are positive. What is the most appropriate initial management?