ReqFingerprint API

GET  /api/config        test parameters + a fresh token
GET  /api/probe         record this connection's IP for ?token= (use on ipv4./ipv6. hosts)
GET  /api/fingerprint   full report (?token=&webrtc=cand1|cand2&trace=0)
POST /api/fingerprint   full report, JSON body {"token":"","webrtc_candidates":[]}