Improve prompt for fiscal year / reporting period

[Greenheart]

• Update the fiscalYear prompt and response schema to extract startDate and endDate, or set to null if nothing was found.

When parsing the result in the fiscalYear job, we should default to startDate ${endYear}-01-01 and endDate ${endYear}-12-31 if the fiscal year is not found.

If the fiscal year is different than ${endYear}-01-01, then we need to treat it as a broken fiscal year, meaning we should reflect this in the reporting period dates, by setting startDate to ${endYear - 1}-MM-DD and endDate to ${endYear}-MM-DD.