The FlexRadio panel, AmpCard and TunerCard each carried their own copy of the
MeterBar (LED-bar) component. Even small drift between the copies made the tuner
meters look slightly off in height/LED size vs the others. Extracted one shared
components/MeterBar.tsx (segments, bar height, padding) and imported it in all
three, so every meter renders at exactly the same size. No behaviour change.
