[Feature]: Show public collection stats in dashboard

### What change would you like to see?

The collection metrics section of the org dashboard should be updated following https://github.com/webrecorder/browsertrix/issues/1051. Details TBD, we'll likely need a new API endpoint to proxy Plausible for logged in users.

### Context

Follows https://github.com/webrecorder/browsertrix/issues/2224