Update to use new `exchange-api` for currencies

[benvaljean]

Describe the bug:

The currency api has had a major version change:

https://github.com/fawazahmed0/currency-api/?tab=readme-ov-file

https://github.com/fawazahmed0/exchange-api/blob/main/MIGRATION.md

Consequently any currency conversion now fails with the error Could not find the currencies.