feat(protocols): add ForcAD HTTP protocol support

[SimoneErrigo]

Adds a dedicated HTTP submission protocol for the ForcAD Attack-Defense CTF (https://github.com/pomo-mondreganto/ForcAD), in cookiefarm/pkg/protocols/forcad_http.go.

The existing cc_http protocol doesn't work correctly against ForcAD: it relies a status field in the checker's JSON response ("ACCEPTED", "DENIED", …), ForcAD's HTTP receiver doesn't send one.

ForcAD's PUT /flags endpoint replies with a JSON array of objects shaped like:

[{"msg": "[] ", "flag": ""}]

There is no explicit status field, the verdict is only encoded in the readable msg. As a result, with cc_http the flag status was never updated.

Tested manually against a running ForcAD instance:

• flags submitted through the gameserver were correctly accepted and their statuses updated in CookieFarm (accepted / denied / service down cases), whereas the same setup using cc_http left the statuses unchanged