cmd/anubis: Give admin-configured failures an "error code" to give to the admins so that genuine users can figure out what went wrong

[Xe]

Ref gitlab.gnome.org/Infrastructure/Infrastructure/-/issues/1921

Maybe this can be implemented by filtering for explicit deny rules and printing a sha256sum of the rule name/regex on application launch so admins can look at the logs and figure out why legit user traffic is failing. It needs to be a hash in order to avoid leaking info to bad actors.

[Xe]

Hacked this up before bed, when Anubis starts up it dumps things to stdout like this:

Rule error IDs:
* amazonbot: 43d21d695d7e7ddf00a97868e9b04ab88f9c6013915531a76081d4f7422a7b96
* us-artificial-intelligence-scraper: 45f2f04635a931264788bb18e68dc50cb9e5e4e3f8ce720c94d5b94c7c2e78d0
* lightpanda: d8a40eef3b9431679ef3463c67aad15edfc974f502772b9d156de3b9363392a5
* headless-chrome: bacf8917032e5a7dfd6df88403e7faaff0c6095a40cca4c422c8489b9332811e
* headless-chromium: 408358af6afdc916ebadd8ba75db5278e4905193b530062660786a10c1b97024

Hopefully this should be enough to figure it out.