A 35-year-old woman from Delhi presents with a 6-month history of persistent dry cough and constitutional symptoms. She is HIV-negative and has no known TB contact. Chest X-ray reveals multiple small nodular opacities (1–2 mm) distributed bilaterally and diffusely throughout both lung fields, with a 'millet seed' appearance. There is no cavitation. Sputum smear microscopy is negative. What is the most likely radiological diagnosis?