Store grid information in config files

The following parameters define the rotated COSMO-2 grid:

```
rlon_first: -6.82
rlon_last: 4.80
drlon: 0.02
rlat_first: -4.42
rlat_last: 3.36
dralt: 0.02
pole_longitude: -170.0
pole_latitude: 43.0
```

They should be stored in a yaml next to the dataset rather than hard-coded in [plotting.py](https://github.com/MeteoSwiss/HiRAD-Gen/blob/f4453421e51d8b89de388443563081e1659fd74d/src/hirad/eval/plotting.py#L11-L12).

Or maybe store the grid info as metadata into the the output, once we switch from torch to zarr?

Start with src/hirad/eval/plotting.py at the hard-coded grid parameters and inspect how the dataset and its outputs are currently loaded. Decide whether the grid belongs in a YAML file next to the dataset or in output metadata when the project moves from torch to zarr. Done means plotting reads the grid information from the selected data source rather than fixed values in plotting.py.

Written by the indexing model from the issue text.