Translations dashboard: only request Weblate data since CSV files were last updated

[hturner]

The Weblate translations dashboard uses the scripts Recent changes.R and User_statistics.R to query the Weblate changes API, process the results and save the tidied data in CSV files.

Unfortunately these scripts currently request all changes since the Weblate server was set up, when we only need the data since the corresponding CSV file or files were last updated. This means the code takes a lot longer than it needs to and uses unnecessary compute resources.

r-devel/translations-dashboard#47 gives some pointers for updating the scripts to be more efficient.

[jimgar]

We are at R Dev Day for Shiny in Production 2025.

So far I have updated Recent changes.R, so it uses the latest dates from the relevant csv files.

We noticed that these dates were still going quite far back (February and March of this year). Heather realised that this is because the Ubuntu runners in the GH Workflow are no longer available, and so the actions have been timing out for the past several months, leaving the csv files unaltered.

I will:

1. Raise a PR to update the runners to ubuntu-latest Update ubuntu runners translations-dashboard#51
2. Raise a PR for Recent changes.R Use csv files for API querying dates translations-dashboard#52
3. Make equivalent updates and raise PR for User_statistics.R