[Referral] Add new teenagers leaderboard

[Luke-Oldenburg]

Summary of the problem

Describe your changes

[sentry]

Bug: Referral::Link objects are incorrectly calling the new_users method, which is only defined on Referral::Program.
_{Severity: CRITICAL | Confidence: High}

🔍 Detailed Analysis

The view code at app/views/admin/new_teenagers_leaderboard.html.erb:16 attempts to call the new_users method on Referral::Link objects. However, the new_users method is only defined on the Referral::Program model, not on Referral::Link. This will result in a NoMethodError at runtime when the page is rendered, causing the server to crash.

💡 Suggested Fix

Refactor the view code to correctly access the new_users method, likely by accessing the associated Referral::Program object (e.g., link.program.new_users) or by defining a similar method on Referral::Link if intended.

🤖 Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: app/views/admin/new_teenagers_leaderboard.html.erb#L16

Potential issue: The view code at
`app/views/admin/new_teenagers_leaderboard.html.erb:16` attempts to call the `new_users`
method on `Referral::Link` objects. However, the `new_users` method is only defined on
the `Referral::Program` model, not on `Referral::Link`. This will result in a
`NoMethodError` at runtime when the page is rendered, causing the server to crash.

_{Did we get this right? 👍 / 👎 to inform future reviews.
Reference ID: 5710073}