Reflashing the Guan Sen WiFi Irrigation Controller with ESPHome

Last summer I was on holiday, thousands of kilometres from home, when I tapped "Pump A: ON" in the Tuya app to give the greenhouse a quick top-up. A few minutes later the WiFi at home dropped. The pumps were still on. I had no way to turn them off. No way to see what was happening. The reservoir was maybe half full, the day was hot and dry, the pumps were inside a wooden greenhouse, and the only…