Add Chromatic visual testing to our site/E2E tests

Chromatic has [introduced visual testing for Playwright](https://www.chromatic.com/playwright). We should explore adding this additional layer of user flow bug detection to our current E2E tests within `site/e2e`.

**Requirements:**

- [ ] Add manual snapshots to each of our E2E tests as appropriate - these can be component snapshots or full page snapshots
- [ ] Remove any redundant storybook component tests (if there are any)
- [ ] Add a NPM script to our `package.json` for running Chromatic with the `playwright` flag
- [ ] Update our CI workflow's Chromatic setup such that it also supports Playwright
- [ ] Update our FE README to make mention of this new tooling
- [ ] Establish baseline speed of our CI run and then compare after we have added this layer - it is important we don't significantly slow down the job considering these tests are run on every PR.
- [ ] Understand monthly cost of these additional snapshots as Chromatic's pricing depends on # of snapshots - is this addition going to move the needle significantly?

Commencez par lire les tests existants dans site/e2e et package.json, puis localisez la configuration actuelle de Chromatic dans le workflow CI. Ajoutez les snapshots Playwright appropriés, le script demandé et la prise en charge de CI, supprimez les tests Storybook redondants et mettez à jour la FE README. Comparez la vitesse de CI avant et après, et documentez le coût attendu des snapshots.

Rédigé par le modèle d'indexation à partir du texte de l'issue.