Is your feature request related to a problem? Please describe.

The RADKLIM dataset is available in netCDF-format at JSC (see #107) and can easily be downloaded at other sites as well from DWD's Opendata server.
To enable training/fine-tuning of the WeatherGenerator with this dataset, a netCDF-dataloader must be implemented.

Describe the solution you'd like

The family of data loaders under src/weathergen/datasets will be complemented by a netCDF data loader.
While the focus is on reading RADKLIM data at first sight, the implementation should also consider possibilities to support reading from netCDF datasets in a more generic way (i.e. minimize hard-coded, dataset-specific assumptions).

Describe alternatives you've considered

The data could be converted to an anemoi-dataset (or to zarr more generally), but this would lead data duplication.

Additional context

The RADKLIM dataset shoudl be used during the hackathon in August 2025.

Organisation

JSC