Killing the boot-time LED flash with a MOSFET

Every power-on, the strip would flash a confused multicolor mess for about half a second before the firmware took over. Not a bug exactly — just the LEDs sitting in an undefined state until the data line settled.

A MOSFET on GPIO21 gates power to the strip until the ESP32 is ready, and the flash is gone.

Small thing, but it’s the difference between “DIY project” and “looks finished.”