A 48-year-old woman from Delhi presents with a 2 cm firm, mobile lump in the upper outer quadrant of the left breast discovered on self-examination 3 weeks ago. On clinical examination, the lump is non-tender, mobile, and there is no skin dimpling or nipple discharge. Axillary lymph nodes are not palpable. Mammography shows a dense mass with irregular margins and microcalcifications. Core needle biopsy confirms invasive ductal carcinoma (IDC). Staging investigations including chest X-ray, abdominal ultrasound, and bone scan are normal. The tumour is ER/PR positive and HER2 negative. What is the most appropriate surgical management for this patient?