referral overhaul

[huumn]

1. every referral link click changes referrer
   • the cookies are already updated, but we'll need to efficiently update the referrer in the database ... we don't want to block rendering or anything to do this
2. referrals count -> active referrals count
3. remove referrals page
4. change referral rules
   • remove referral payouts on boost/jobs
   • keep referral payouts on zaps
   • add 2.1% referral payout on rewards
     • that is, when their referees earn rewards, give 2.1% of those rewards to their referrer