FireWatch: Forecast/prediction source info

**Describe the task**
Add info about what data is being used to project indices forward.

`About this data`? Something else?

**Acceptance Criteria**
- [ ] first
- [ ] second
- [ ] third

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

The issue does not name any files, tests, entry points, or forecast view. First clarify which projected indices and data sources need attribution, then locate the code that presents those projections and define concrete acceptance criteria for the displayed source information.

Written by the indexing model from the issue text.