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?

まず site/e2e と package.json にある既存のテストを読み、次に CI ワークフロー内の現在の Chromatic セットアップを見つけます。適切な Playwright スナップショット、要求されたスクリプト、CI サポートを追加し、重複している Storybook テストを削除して、FE README を更新します。変更前後の CI の速度を比較し、想定されるスナップショットのコストを文書化します。

索引モデルが issue の本文から書いたものです。