Bringup valve-controller PCBA

[Poofjunior]

Upon receiving the prototypes from PCBWay (~eta Mar 17), we need to validate that:

• the board powers on
• we can upload firmware
• we can apply hit-and-hold control to all valve outputs
• we can read all AUX GPIOs set as INPUTs
• we can write values to AUX GPIOs set as OUTPUTs

We'll need to merge #4 first or use the firmware from that branch.