A 19-year-old woman presents with a 3-day history of dysuria, increased urinary frequency, and urgency. She has no fever or loin pain. A urine dipstick is positive for nitrites and leucocytes. She is not pregnant and has no known drug allergies. This is her first such episode. According to NICE guidance, what is the recommended duration of antibiotic treatment for uncomplicated lower UTI with trimethoprim or nitrofurantoin in this patient?