HFI Calculator: Mark a fuel type as changed (similar to wind speed in FB Calc.)

**As a** *Plans/R/ZWCO* **I want** *clarity on non/default fuel types* **So That** *I can keep track of my changes*

users say: it's hard to remember / notice when I made a change, e.g. a fuel type (usability heuristic - recognition over recall). Anxiety that other people are making changes and I won't know.
- user suggestion: label which fuel types are default (this is challenging in the UI and differs by FC)

simple & quick solution without much thought (heavy disclaimer)
- highlight a fuel type cell when it differs from the default fuel type for the station - similar to wind speed in FB Calc.
- add a reset / return to defaults button

it needs to be included in the PDF export

**Additional Context**
- enter text here
- enter text here

**Acceptance Criteria**
- [ ] Given (Context), When (action carried out), Then (expected outcome)
- [ ] Given (Context), When (action carried out), Then (expected outcome)

**Definition of Done**
- Ready to Demo in Sprint Review
- Does what I have made have appropriate test coverage?
- Documentation and/or scientific documentation exists and can be found
- Peer Reviewed by 2 people on the team
- Manual testing of all PRs in Dev and Prod
- Merged

The issue does not identify files, tests, or entry points, so first locate the HFI Calculator fuel-type UI and the PDF export path. Read how default fuel values and the comparable wind-speed change indicator are handled. Done means changed fuel types are visibly marked, can be reset to station defaults, and the marking appears in PDF output with appropriate tests and documentation.

Written by the indexing model from the issue text.