Internal: Run heavy redis data refresh in workers, minor fix on teacher page

• Teacher stats table header columns were wrong after a past update, they were fixed
• Internally, running heavy daily computations in worker processes by using BullMQ. This utilizes queues via redis, which prevents adding duplicate jobs if they exist in queue or are worked on already. The jobs are added by a cron job every day at 1 am. Notice that "all teacher leaderboards" is not ran in a job yet (it was not ran regularly previously either).
• The jobs can also be added via updater page in frontend. The page also shows currently running jobs.
• The backend should now be scalable to multiple instances