fix(mailer): use DOMAIN env var for email links

[Ronnie434]

Summary

• Replace hardcoded email verification and password reset URLs in iowrappers/mailer.go with the DOMAIN environment variable
• Removes environment-specific branching (testing vs production) in favor of a single config-driven approach
• Falls back to http://localhost:10000 for local development
• Fix Jest CI to pass with --passWithNoTests

Motivation

The previous implementation had hardcoded URLs (www.unwind.dev for production, testing-vp.herokuapp.com for testing). This made it fragile when deploying to different environments. Using the DOMAIN env var (already used elsewhere for OAuth config) makes it consistent and portable.

Test plan

• Verify email verification flow works in production
• Verify password reset flow works in production
• Confirm localhost fallback works for local development

[tim-eternos]

LGTM