Add random API key selection strategy (random) for routing

[kagorec]

Hello,

I would like to suggest adding an alternative to the default routing strategy. As I understand it, requests are currently routed sequentially using a round-robin approach. It would be very useful to have an additional mode where the API key is selected randomly from the available list.

This would be especially helpful when working with a large number of keys, as it could distribute token usage more evenly across them. In my case, under heavy usage, the first 10 out of 100 API keys were blocked fairly quickly, even though the total key pool is much larger.

It would be great if CLI-PROXY-API supported a random strategy in the routing configuration, for example:

config.yaml:

routing:
  strategy: "round-robin" # round-robin (default), fill-first, random

Thank you for considering this feature request. I believe it would be very useful for users managing a large set of API keys.