A silent printer no longer blocks printing or reports as unhealthy. printPng
returns confirmed:false when no status came back, so callers don't claim a
label came out when all we know is the bytes were delivered.
Takes the PNG renderBadgePng already produces, separates black and red
planes, and sends the job over TCP. Adds a serial queue per printer host so
simultaneous sign-ins cannot collide on the printer's single connection.
Not wired into printer.js yet.