Update s2 cloudless basemap to correspond with the 'year' in the time tab

[cholmes]

Now that there's very clear control of the year via the new time tab it'd be nice to have the basemap reflect that. S2 cloudless has a number of years, so it'd be great to just change the basemap as users change the year, so the results can be instantly compared to the year they were made with.

[zrichardet]

@cholmes There's no s2 cloudless layer for 2025 yet. It is supposed to be available early 2026. How should we handle the case when the user selects 2025 from the year selection?

[m-mohr]

This is implemented, but we need to update the implementation to include 2025 once available.