A 33-year-old woman with a known history of HIV infection, diagnosed several years prior, presents to her routine outpatient follow-up appointment reporting the gradual onset of unusual skin lesions over the past month. She describes them as initially small, reddish-brown spots that have slowly grown and become darker, some appearing raised. She notes intermittent adherence to her prescribed antiretroviral therapy due to personal circumstances. Her most recent laboratory work-up, performed two weeks ago, revealed a CD4+ T-cell count of 185 cells/mm^3. She denies fever, chills, night sweats, significant weight loss, or gastrointestinal symptoms, though she has noticed some mild discomfort when swallowing larger food items recently. Her vital signs today are: temperature 37.0°C, blood pressure 118/74 mmHg, pulse 88/min, respirations 14/min, and oxygen saturation 98% on room air. Physical examination reveals multiple, non-blanching, violaceous to brownish-purple plaques and nodules of varying sizes distributed across her trunk, upper extremities, and lower extremities. A few similar lesions are noted on the oral mucosa, specifically on the hard palate. There are no signs of active bleeding or ulceration. Considering her clinical presentation, what is the most likely diagnosis and the appropriate initial management strategy?