chore(settings): remove redundant React imports

[vbudhram]

Because

• The jsx: react-jsx transform means import React from 'react' is no longer needed for JSX
• The recent Storybook upgrade dropped the last build constraint that still required it

This pull request

• Drops the default import React from 'react'; line from files in packages/fxa-settings where the React namespace wasn't used
• Rewrites React.* references as named imports in six stories that still relied on the namespace: BoxButton, ButtonPasskeySignin, CardHeader, Settings/Modal, Settings/ModalVerifySession, and .storybook/preview.tsx
• Some unrelated files got minor Prettier reformatting from the repo's lint-staged hook on commit

Issue that this pull request solves

Closes: https://mozilla-hub.atlassian.net/browse/FXA-13744

Checklist

Put an x in the boxes that apply

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).
• I have manually reviewed all AI generated code.

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[vbudhram]

@LZoog tests pass and storybook work 👍🏽