Update CNAME value to b7278b3c9357963d.vercel-dns-013.com in custom domain documentation

[devin-ai-integration]

Update CNAME value to b7278b3c9357963d.vercel-dns-013.com in custom domain documentation

Summary

Updated the CNAME value in the custom domain setup documentation from a placeholder [unique CNAME value provided by Fern] to the specific value b7278b3c9357963d.vercel-dns-013.com. This affects two sections in the documentation:

1. Subdomain setup (line 45)
2. Root domain setup (line 145)

Review & Testing Checklist for Human

• Verify CNAME value is correct: Confirm that b7278b3c9357963d.vercel-dns-013.com is the intended CNAME value to show in documentation examples
• Check documentation consistency: The surrounding text still mentions "Contact Fern... to receive: A unique CNAME value for your site" - verify this is still accurate or if it needs updating to reflect that customers now use this standard value
• Preview rendered documentation: Check that the documentation renders correctly on the preview site, especially the code blocks showing the DNS records

Notes

• The change replaces generic placeholder text with a specific Vercel DNS endpoint, suggesting a possible shift from per-customer unique CNAME values to a standardized value
• No other documentation text was updated, so the messaging around "unique CNAME values" remains unchanged
• Requested by danny@buildwithfern.com (@dannysheridan)
• Link to Devin run: https://app.devin.ai/sessions/bcd88df446b444c7b6c3c75d4ae2c5d6

[devin-ai-integration]

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