A 34-year-old woman presents to the Emergency Department with a severe headache, photophobia, and neck stiffness. A lumbar puncture is performed. Cerebrospinal fluid (CSF) analysis shows: Appearance: Turbid, Glucose: 1.5 mmol/L (Serum glucose: 5.5 mmol/L), Protein: 1.8 g/L, White cell count: 800 cells/µL (90% neutrophils). What is the most likely diagnosis?