feat: implement DNS server fingerprinting (HAN-384) (#10)

internal/output/formatter.go

@@ -30,6 +30,10 @@ type Config struct {
 	Quiet              bool
 	Color              bool
 	Debug              int
+
+	// Fingerprints maps server IP strings to their version.bind version strings.
+	// Populated by RunTraversal when ShowVersions and ShowServers are both true.
+	Fingerprints map[string]string
 }
 
 func DefaultConfig() *Config {