ESP32 freezer alarm: a DS18B20 probe that emails you when the freezer warms up

This is a simple, adaptable build pattern rather than a polished product: an ESP32 reads a waterproof DS18B20 probe and sends an email alert when the temperature goes over your setpoint, then another when it comes back down. Fishrider24's version (the README credits the code and its modifications to Evan Potts, starting from Random Nerd Tutorials examples) updates the code for ESP32 Arduino core 3.x and adds a Wi-Fi setup portal, so you set the Wi-Fi, email sender, timezone, Fahrenheit or Celsius, an optional InfluxDB 1.8 server and even the probe's GPIO pin from a web page instead of in code. The author uses GPIO 4. Version 2.4 added OTA updates (change the default password), and 2.6 shows the last ten email successes or failures on the main page so a broken mail setup doesn't go unnoticed. It sends through Gmail with an app password by default. Why it matters in an outage: Ready.gov says a full freezer keeps its temperature for about 48 hours if you keep it closed, and to throw food out if it reaches 40 °F or higher. An alarm tells you when you're getting close. The ESP32 and your router both need power and internet to send the email, so put them on a UPS or power bank if you want alerts during a power cut. The README notes that AT&T no longer delivers email-to-text, and Verizon is expected to drop it, so use a normal email inbox with notifications.