Allow switching climate risk tertiles between national and city-level

[kaushik12]

Currently the climate risk tertiles (High/Med/Low) are based on the national distribution of the risk scores. This is relevant in some circumstances such as understanding if the city has significant risk from a particular type of disaster, but perhaps in the context of prioritization within a city, one might be interested in understanding where the highest climate risks are within the city.

Tasks:

• Backend: Additional columns for climate risk to include city-level tertiles
• Frontend: An easy UI element to switch the respective column to use