Auth users: Show number of credits remaining on the brick cover page

[SashaScholar6]

• [x] on hover, number of credits (eg.3) becomes feather-play icon

[ivanromakh]

@SashaScholar6 you mean show number of brills? for authorized users?

[SashaScholar6]

No this is credits (which are worth 100 brills), but we'll clarify tomorrow with @aromakh and @lindsaymacvean