fix: export email list response type

[Shubhdeep12]

• Exports the email list response interface from the public barrel so consumers can type emails.list responses.
• consistent with other list endpoints.

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Summary by cubic

Exported the list-emails options interface from the public emails barrel so consumers can type emails.list calls. This fixes the missing export and keeps consistency with other list endpoints.

^{Written for commit f33d812. Summary will update on new commits.}

[cubic-dev-ai]

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