A 68-year-old woman with chronic kidney disease (eGFR 28 mL/min/1.73 m²) and type 2 diabetes mellitus undergoes emergency repair of a perforated duodenal ulcer. On postoperative day 12, the surgical wound shows delayed epithelialization with minimal granulation tissue formation. Serum creatinine is 3.2 mg/dL, and vitamin C level is 0.4 mg/dL (normal: 0.6–2.0 mg/dL). Which phase of wound healing is MOST SIGNIFICANTLY impaired in this patient?