Introduces WhitelistedAuthenticator that wraps an auth.Authenticator to skip
authentication when the client IP matches configured CIDR ranges or exact IPs.
The wrapping happens at service-parse time, transparently covering all handler
types (HTTP, SOCKS4/5, relay, http2, SSH).
Usage:
gost -L 'user:pass@:5999?skipauth=192.168.0.0/24,172.22.22.22/32'
ginuerzh