A 4-year-old girl from rural Maharashtra presents with a 3-month history of low-grade fever, failure to thrive, and persistent cough. Her mother reports contact with a grandmother who was recently diagnosed with sputum-positive pulmonary tuberculosis. On examination, the child appears malnourished (weight 12 kg, height 95 cm). Chest X-ray shows a right hilar lymphadenopathy with no parenchymal consolidation. Tuberculin skin test (Mantoux test) shows an induration of 12 mm at 48 hours. Sputum smear microscopy is negative for acid-fast bacilli. What is the most appropriate diagnosis?