Morecast: Better Error Messages

[conbrad]

Describe the task We currently only show generic error messages in Morecast that have no context. This causes frustration for users that want to fix issues in their draft forecasts but don't have enough details. Morecast should include frontend validation for each forecast cell and provide specific instructions to the user so they can fix any. If any errors are unrecoverable this should be a separate error.

Acceptance Criteria

• [ ] Identify all validation conditions that currently exist in WF1 weather forecasting backend
• [ ] Match the above with frontend validation for each cell as cells are edited in Morecast
• [ ] Frontend validation should include helpful error messages so users can fix any problems they have control over
• [ ] Any errors that come back from WF1 when posting a forecast should be shown to the user in a way that makes it clear that there is nothing the user can do to fix the issue and that they should contact us in this case.
• [ ] Flag error that can occur when a station is missing actuals as this will block submission of a forecast (submitting forecasts in PR deployments is blocked if any 'actual' rows are present

Additional context

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