Archive sources with archive.org

We should integrate https://archive.org/web/ to prevent dead links.

# Specifications

## Backend

- [ ] When adding a source, ping webarchive's API to ask for the URL to be indexed

## Frontend

On the source, add an icon in the top-right corner of the sources

- [ ] Icon: `styled-icons/fa-solid/Archive`
- [ ] Title: 'View archived version'
- [ ] Link to the page on WebArchive, at the closest date from `insertedAt`

---

*Suggested by zurbo*

Start by locating the backend flow that adds a source and the frontend component that renders source actions. Read the Web Archive API documentation and trace how `insertedAt` is stored and displayed. Done means new sources are submitted for indexing and each source shows an archive icon linking to the closest archived version.

Written by the indexing model from the issue text.