A 28-year-old woman from Delhi presents with a 6-month history of arthralgia affecting the small joints of both hands, morning stiffness lasting 2 hours, and a malar rash that worsens in sunlight. She reports recurrent oral ulcers and has noticed hair loss over the past 3 months. Laboratory investigations reveal: ANA 1:640 (homogeneous pattern), anti-dsDNA antibodies positive (180 IU/mL), anti-Smith antibodies positive, complement C3 66 mg/dL (normal 90–180), C4 12 mg/dL (normal 16–38), and urinalysis shows 2+ proteinuria with RBC casts. Which of the following is the most likely diagnosis?