[HW] Power bench: TP4056 + MT3608 + battery — 5V bus in both modes

[AldoSeffrin]

DEVELOPMENT_PLAN §1.3 (Power architecture). First electronics session.

Scope

• Solder battery connector adapter JST-XH-2P → JST-PH 2.0 (PH kit in stock)
• TP4056 (USB-C input) + 1S2P 5200 mAh battery on B+/B−
• ⚠️ MT3608 before first use: trimpot ~20 turns CCW, multimeter on VOUT, adjust slowly to 5.0 V — only then connect to the circuit (overvoltage kills ESP32/ADS1256)
• On/off button on the 5V bus
• Test both modes: USB-C direct and battery→MT3608

Gate: stable 5.0 V on the bus in both modes.

Ref: docs/DEVELOPMENT_PLAN.md §1.3 power architecture + electronics checklist.