Add user privacy check to hide FollowUserButton for private users

[HuanFengYeh]

Summary

This PR adds a user privacy check to the TestimonyHit component to hide the FollowUserButton for private users.

Checklist

• On the frontend, I've made my strings translate-able.
• If I've added shared components, I've added a storybook story.
• I've made pages responsive and look good on mobile.

Screenshots

Known issues

The hit.public field is assumed to be available in the search index.

Steps to test/reproduce

1. Go to the home page
2. Logged in as a user who can follow others.
3. Go to the browse testimony page
4. Confirm that the Following Button is displayed for that private user.

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
maple-dev	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 14, 2025 0:45am
maple-prod	🔄 Building (Inspect)	Visit Preview	💬 Add feedback	May 14, 2025 0:45am

[Mephistic]

LGTM