Replace API with index SQL

[okwme]

first query to index API is implemented in store/sql.js. Can follow suit and replace the entire API.

subscriptions queries

• todays leaderboard (confirm whether it's better to subscribe to multiple queries or make one big query)
  • fastest query
  • slowest query
  • streak? (maybe could be as needed since it changes so seldomly)
  • today's levels
• current address balance (?)

as needed queries

• previous leaderboard
• leaders who claimed their free mint (done)