A 58-year-old man from rural India presents with progressive dysphagia and epigastric pain for 4 months. Upper endoscopy reveals a 5 cm ulcerated lesion in the gastric antrum with biopsy-confirmed adenocarcinoma. CT chest and abdomen shows no distant metastases, but there is thickening of the gastric wall with regional lymph node involvement (T3N2M0). The patient is fit for surgery with good performance status. What is the most appropriate next step in management?