It’s not even 8:30 on a Monday night, and already a good quarter of the roughly 200-person audience crammed within the converted courtyard that is Bardot’s stage for the weekly School Night concert series is bouncing around, drenched with sweat like it’s an all-night warehouse rave. “C.E.A.R.T.A.,” they all scream in unison, spelling out the Irish word for “rights” and …