A 58-year-old man from Mumbai presents with progressive dyspnea on exertion for 8 months and a dry cough. He is a retired stonemason with 35 years of occupational exposure. On examination, he has bilateral fine crackles at the lung bases. High-resolution CT chest shows bilateral lower-lobe predominant reticular opacities with traction bronchiectasis and honeycombing. Pulmonary function tests reveal FVC 62% predicted, FEV₁/FVC ratio 0.78, and DLCO 45% predicted. What is the most likely diagnosis?