Power off drops the peripheral rail (PWR_ON low), sleeps the panel and
puts the chip into deep sleep with ext1 wake armed on the encoder pins,
choosing any-low or any-high from the knob's resting state so a single
detent wakes it. The button (GPIO0) is not a wake source on purpose.
ESP-IDF 5.5 + LVGL 9 firmware that plays random public cameras from
insecam.org on the T-Embed's 320x170 screen, live MJPEG where available,
a new camera every 20 seconds. Knob steps through cameras, LED ring shows
the countdown. Auto-detects the original vs CC1101 board, reuses Wi-Fi
credentials from NVS and falls back to a captive-portal setup hotspot.