New feature (before winter hits)
* [x] better graph using `highchart`
* [x] add option to store temperature and relay state on every tick in `influxdb`
* [x] leverage `influxdb` aggregation to get daily/weekly/monthly graph (mean)
* [x] better config validation (using `pydantic`)
* [x] make sure the code can run "not-on-a-pi" to speed up dev (in that case temperature readings are random-ish)