chore: update readme with receiver board pad legend

chore: fix artifact paths "If a wildcard pattern is used, the path hierarchy will be preserved after the first wildcard pattern" https://github.com/actions/upload-artifact/blob/c40c16d999899d3642ba1597014ba7ef8ff611e7/README.md\#upload-using-multiple-paths-and-exclusions

chore: update KiCad dates

chore: add workflow to export gerbers, pending kikit docker images

chore: update component placement for kikit 1.7.0

chore: unify and automate gerber scripts

chore: clean up 3d models

chore: update board images

chore: misc cleanup

chore: remove old step files