Replace latestAnomalyDate with repo based anomalyDate to support updates without rebuilding.

[SiggyF]

The latestAnomalyDate is now retrieved from netlify environment during build time.

This date can change when data is updated. So we want to move this date somewhere outside of the built environment, preferably by retrieving it from mapbox.

When this is available we should be able to use the repository pattern, similar to applied in the reservoir repo. Then we can inject it into the appropriate place in the MapLayers panel. That should allow us to update date dynamically without rebuilding

[Jaapel]

Example tileset_source call: https://api.mapbox.com/tilesets/v1/global-water-watch using the access_token with proper scopes.