A 52-year-old man from Delhi presents with a 6-month history of a pigmented lesion on his left shoulder. On examination, the lesion measures 8 mm in diameter with irregular borders, color variegation (brown, black, and red), and mild surface ulceration. Dermoscopy shows asymmetry, atypical network pattern, and blue-white veil. Excision biopsy confirms melanoma with a Breslow thickness of 2.4 mm, 3 mitoses per mm², and no ulceration on histology. Sentinel lymph node biopsy is negative. What is the AJCC TNM stage of this melanoma?