A 20-year-old female presents with dizziness, fatigue, facial edema, polyarthralgia, hair loss, and oral ulcers for 5 months. Previously diagnosed with 'nephritis' but treatment was ineffective. Anemia worsened after whole blood transfusion. ESR 120mm/h, WBC 4.5×10<sup>9</sup>/L, RBC 2.5×10<sup>12</sup>/L, Hb 50g/L, platelets 5.5×10<sup>9</sup>/L, reticulocytes 10%. Urinalysis: RBC 5-8/HP, urinary protein (++++), hyaline casts (+), granular casts (+). The most likely diagnosis is: