What does this PR do?

Updates @dub/analytics package to support domainsConfig.refer for client-side click tracking.

<DubAnalytics
  ...
  domainsConfig={{
    refer: "refer.cal.com",
  }}
/>

Also adds a reverse proxy to ensure tracking accuracy.

Testing

To test this, follow these steps:

1. Go to the signup page with a ?via= param appended (e.g. https://app.cal.com/signup?via=steven)
2. Check the Network tab to see a /track/click network call, and see that a dub_id cookie was set
3. Make sure the click is tracked in the Events tab on Dub

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.