A 20-year-old female presents with recurrent high fever, migratory arthralgia, oral ulcers, and hair loss for 1 month. Investigations show RF 1:20(+), anti-SSA antibody (+), anti-dsDNA antibody (+), urinary protein (++), and 5 granular casts/HPF. Renal biopsy reveals diffuse proliferative nephritis. The best first-line drug combination is: