fix: prevent domain-like usernames from becoming links

[devin-ai-integration]

Prevents usernames with '.' from auto-linking in verification emails.

Changes:

• Updated sanitizeDisplayName function to detect and transform domain-like patterns
• Applied sanitization to verification email templates
• Replaces dots with '[dot]' in usernames to prevent auto-linking

[Link to Devin run: https://app.devin.ai/sessions/20a54ba5d52342b999a68700e5889a75]

[devin-ai-integration]

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[graphite-app]

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