docs(auth): warn users about sms usage

[MichaelVerdon]

Description

Warn users in documentation that sms it not considered 'secure'. Not mentioned in Native Docs.
Noted here:

• https://www.cisa.gov/sites/default/files/2024-12/guidance-mobile-communications-best-practices.pdf
• https://cloud.google.com/solutions/modern-password-security-for-system-designers.pdf

Related Issues

closes #17202

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