A 49-year-old man is newly diagnosed with type 2 diabetes mellitus after HbA1c 7.8% (62 mmol/mol). He has no established CVD, eGFR 82 mL/min/1.73 m², BMI 32 kg/m² and is motivated to change lifestyle. According to the RACGP-Diabetes Australia handbook, what is the most appropriate initial pharmacological treatment?