Add BE: NWP

[peterdudfield]

Save BE ECMWF and Metoffice

Detailed Description

It would be good to save an option to NWP data for Beligum

Context

• Exampling to new country

Possible Implementation

• TODO

[Raakshass]

Hi @peterdudfield! I'd like to work on this issue.

My approach:

1. Study the existing NWP implementations (e.g., UK, DE) in the codebase
2. Research Belgium ECMWF and Met Office data endpoints/formats
3. Implement the BE NWP fetcher following the established patterns
4. Add tests and documentation

I'll start by exploring the codebase and will open a draft PR soon. Let me know if there are any specific requirements or pointers!