Load email otp component as 2fa fallback

What does this MR do and why?

Allow Email OTP to be used as a fallback option for TOTP.

Part 2 for https://gitlab.com/gitlab-org/gitlab/-/issues/570174.

References

Related: https://gitlab.com/gitlab-org/gitlab/-/issues/570174

Screenshots or screen recordings

Scenario	Reocrding	Comment
User failed Webauthn and is permitted to use email OTP as fallback	Screen_Recording_2025-11-06_at_1.38.05_PM	User can click links in the Webauthn footer, the 2nd link allows user to send email OTP to complete verification ✅
User failed Webauthn, chooses TOTP verification instead, and is permitted to use email OTP as fallback	Screen_Recording_2025-11-06_at_1.54.41_PM	User can send OTP to email as fallback verification and complete the login process ✅
User failed Webauthn but is not permitted to use email OTP as fallback	Screen_Recording_2025-11-06_at_1.42.43_PM	the send OTP to email link is not available to user as fallback for neither webauthn nor TOTP ❌
User only has TOTP enabled, and is not permitted to use email OTP as fallback	Screen_Recording_2025-11-06_at_1.47.11_PM	The send OTP to email link is not available to user as fallback under the TOTP form ❌
User only has TOTP enabled, and is permitted to use email OTP as fallback	Screen_Recording_2025-11-06_at_1.49.32_PM	User can send OTP to email as fallback verification and complete the login process ✅

How to set up and validate locally

MR acceptance checklist

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