dhcgn/iot-ephemeral-value-store — reverse-engineered prompt

Build me a small self hosted IoT value store server in Go.

I want simple devices like Shelly, ESP32, or Home Assistant to send sensor values with basic HTTP GET URLs, like temperature and humidity in query parameters. The server should create a key pair, one upload key for writing data and one download key for reading it, so I can safely share read access without letting people change values.

The stored data should be temporary and expire after a configurable time, like 24 hours. Let me read everything back as JSON, or fetch individual values as plain text. It should also handle updates that can build up a nested JSON object over time.

Please include a simple web page with usage examples, server stats, and a viewer where I can paste a download key and watch current values. Make it easy to run locally or in Docker, with local embedded storage and basic tests.