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.
