Make the default run list filters more explicit

[myftija]

In the /runs API endpoint we apply a time range filter (last 7 days) by default. This is not obvious in the API docs or in the SDK runs.list method, which can lead to confusion.

We should document this behavior in the docs. Additionally it might be reasonable to add the applied filters as metadata in the API response.

Similarly in the runs page in the dashboard, we can hint at changing the default time range filter when there are no runs returned for the selected filters.