HFI Calculator: What is BL? users are asking

**Describe the task**
Coastal use an unofficial BL fuel type - we introduced a compromise or 'close enough' fuel of M2 25% Conifer but labelled it as BL in the HFI interface. Users (incl. Coastal users) are confused: "what is BL" "which fire centre is this for?"

**Acceptance Criteria**
- [ ] modify BL label e.g. BL (M2 25% Conifer) - or just tell them to use M2 25%? #1658 for history
- [ ] training / awareness opportunity for PO?
- [ ] users also ask how to get the actual BL validated and into our products

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

Start in the HFI Calculator interface by locating the BL fuel-type label, then read issue #1658 for the history behind the compromise. Confirm whether the accepted outcome is a clearer label or guidance toward M2 25% Conifer; done means users can identify what BL represents and its intended context.

Written by the indexing model from the issue text.