Add translations for email responses

This project supports Spanish and Mandarin language options, which we have setup using `react-18next` on the frontend for static text. However, we should also support translated text in the email responses for user authentication. Note: we should use COSA as a reference to implementing translated emails

Start by locating the authentication email response implementation and the existing react-18next translation setup. Compare the approach used by COSA, then verify that authentication emails support the project's Spanish and Mandarin language options.

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