A 58-year-old man from rural Maharashtra presents with a 4-month history of progressive dysphagia, early satiety, and weight loss of 8 kg. Upper endoscopy reveals a 5 cm ulcerated lesion in the gastric antrum with irregular margins. Biopsies confirm adenocarcinoma. CT staging shows a T3N2M0 tumour with no distant metastases. The patient is fit for surgery with normal renal and hepatic function. What is the most appropriate next step in management?