Dev: Dedup WeatherStation Models

**Describe the task**
There are similar/same `WeatherStation` model definitions in:
`wps_shared/schemas/hfi_calc.py` and `wps_shared/schemas/stations.py`

**Acceptance Criteria**
- [ ] Merge and use a single definition of `WeatherStation` for these two definitions

**Additional context**
- Add any other context about the task here.
- Or here

Compare the WeatherStation definitions in wps_shared/schemas/hfi_calc.py and wps_shared/schemas/stations.py, then trace their uses to determine which definition should be shared. Done means both locations use one WeatherStation definition and the existing behavior remains intact.

Written by the indexing model from the issue text.