See below. The pre-requisite is that hub login security has to be turned off (under Settings -> Hub Login Security). Replace hub.ip.addr with the actual address of the hub. I don't know this for a fact, but I would bet that 127.0.0.1 (loopback address) would work.
This is the rule to reboot at 4AM every day:
Note that the HTTP request has to be a POST request (not an HTTP GET):
