A 58-year-old Indian man with a 10-year history of type 2 diabetes mellitus presents with progressive lower limb edema, foamy urine, and dyspnea on exertion for 2 months. On examination: BP 156/94 mmHg, bilateral pitting ankle edema, bibasal crackles on auscultation. Urine dipstick: 4+ protein. Serum creatinine 2.8 mg/dL, albumin 2.4 g/dL, total cholesterol 285 mg/dL, HbA1c 9.2%. Urine microscopy shows no RBCs, no casts. Renal ultrasound shows normal-sized kidneys with increased echogenicity. What is the most likely diagnosis?