STAT3 and chronic obstructive pulmonary disease: Zhuye Shigao Decoction Combined with Qingqi Huatan Pills in Alleviating the Acute Exacerbation of Chronic Obstructive Pulmonary Disease (Phlegm-Heat Stagnating in the Lungs) via the IL-6-Mediated JAK1/STAT3 Signaling Pathway