Bug: Multiple authors and affiliations fails

[luismmontilla]

Bug description
When specifying multiple authors with affiliations (including both index and id fields as per documentation), the template throws the error:

error: dictionary does not contain key "index"
    ┌─ @preview/pubmatter:0.2.1/pubmatter.typ:270:30
    │
270 │         super(str(affiliation.index))
    │                               ^^^^^

To Reproduce
Steps to reproduce the behavior:

1. Use the following YAML front matter in a Quarto document:

     title: "Mathematical Theorems"
     abstract-title: Theorems
     authors: 
       - name: Jane James
         orcid: 0000-0000-0000-0000
         affiliations: 
           - name: University of A 
       - name: Jhon Jones
         orcid: 0000-0000-0000-0000
         affiliations: 
           - name: University of B
      ´´´

Alternatively:

```yaml
authors: 
  - name: "Author One"
    orcid: "0000-0000-0000-0001"
    email: "author1@domain.edu"
    affiliations: 
      - id: "AFF1"
        index: 1
  - name: "Author Two"
    orcid: "0000-0000-0000-0002"
    affiliations: 
      - id: "AFF1"
        index: 1
affiliations:
  - id: "AFF1"
    index: 1
    name: "Institution Name"
```

2. Render the document with lepub-typst format.

Expected behavior
The document should render with authors and their affiliations correctly displayed.

Actual behavior
Rendering fails with the error above.

Environment

• Quarto version: 1.7.31
• lepub-typst version: [your version]
• OS: MacOS 15.1.1

Additional context

• I have confirmed that both id and index are specified in the authors' affiliations and the main affiliations list.

[roaldarbol]

Hi @luismmontilla!

Thanks for testing out the template! I know there's still a few things that do not work, and this seems to be one of them - so really great to have the issue documented. I'm currently travelling, but I'll get back to this in October! If that's too long, please feel free to make a PR, I'll have time to do a brief test and review. :-)