A 52-year-old male laborer presents with acute-onset low back pain radiating to the right lower limb for 3 days. He reports difficulty walking and numbness in the right foot. On examination, he has a positive straight leg raise test at 35°, diminished right ankle reflex, and weakness of right foot dorsiflexion (grade 3/5). MRI lumbar spine shows a large central-right posterolateral disc herniation at L4–L5 level with nerve root compression. Which of the following is the most appropriate immediate management?