A 38-year-old male worker in a textile mill presents with progressive dyspnea, dry cough, and chest tightness for the past 3 years. He works in the cotton processing unit for 8 hours daily. On examination, he has reduced breath sounds bilaterally with fine crackles at both lung bases. Chest X-ray shows bilateral lower lobe predominant reticular opacities with 'eggshell' calcification of hilar lymph nodes. Pulmonary function tests reveal a restrictive pattern with FVC 65% predicted and FEV₁/FVC ratio 0.82. What is the most likely diagnosis?