feat: 16 funciones cybersecurity — análisis, crypto e IO de seguridad

12 funciones puras con implementación real:
HashSHA256, HashMD5, EntropyShannon, IsBase64, IsHex, ExtractURLs,
ParseIPCIDR, IPInRange, NormalizeURL, DetectSQLInjection,
LevenshteinDistance, JaccardSimilarity

4 funciones impuras con implementación real (stdlib):
LookupWhois, ResolveDNS, FetchHTTPHeaders, ScanPortTCP

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

functions/cybersecurity/lookup_whois.go

@@ -0,0 +1,33 @@
+package cybersecurity
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"strings"
+	"time"
+)
+
+// LookupWhois realiza una consulta WHOIS para el dominio proporcionado conectandose al servidor whois.iana.org.
+func LookupWhois(domain string) (string, error) {
+	conn, err := net.DialTimeout("tcp", "whois.iana.org:43", 10*time.Second)
+	if err != nil {
+		return "", fmt.Errorf("error conectando al servidor WHOIS: %w", err)
+	}
+	defer conn.Close()
+
+	_ = conn.SetDeadline(time.Now().Add(10 * time.Second))
+
+	_, err = fmt.Fprintf(conn, "%s\r\n", domain)
+	if err != nil {
+		return "", fmt.Errorf("error enviando consulta WHOIS: %w", err)
+	}
+
+	var sb strings.Builder
+	_, err = io.Copy(&sb, conn)
+	if err != nil {
+		return "", fmt.Errorf("error leyendo respuesta WHOIS: %w", err)
+	}
+
+	return sb.String(), nil
+}