AirVisual AQI values need a standard and an observation time

IQAir's API documentation distinguishes aqius and aqicn, and weather observations need not share the pollution observation's timestamp.

For the AirVisual integration, display the selected AQI standard beside the value and keep the relevant observation time attached. Test a response whose weather and pollution timestamps differ. A fresh weather update must not make an older pollution reading look new, and a regional measurement is not a guarantee of an individual's immediate exposure.