add initial Go implementation of arcline-audit

Implements the full site health auditor with four check groups:

  - SSL/TLS (certificate validity, expiry, chain, TLS version, ciphers)

  - HTTP (redirect chain, security headers, response time)

  - DNS (A/AAAA, MX, SPF, DKIM, DMARC, DNSSEC)

  - Infrastructure (CDN detection, common port probes)

Includes CLI with --checks filter, --json and --out flags,

cross-compile Makefile, and GitLab CI pipeline.

Signed-off-by: Blake Ridgway <blake@blakeridgway.com>

cmd/arcline-audit/main.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"net"
+	"os"
+	"time"
+
+	"arcline-audit/internal/dns"
+	httpcheck "arcline-audit/internal/http"
+	"arcline-audit/internal/infra"
+	"arcline-audit/internal/report"
+	"arcline-audit/internal/ssl"
+	"arcline-audit/internal/types"
+)
+
+func main() {
+	checksFlag := flag.String("checks", "all", "comma-separated list of checks: ssl,http,dns,infra")
+	jsonFlag := flag.Bool("json", false, "output as JSON")
+	outFlag := flag.String("out", "", "write report to file")
+	flag.Parse()
+
+	if flag.NArg() < 1 {
+		fmt.Fprintf(os.Stderr, "Usage: arcline-audit [flags] <domain>\n")
+		fmt.Fprintf(os.Stderr, "\nFlags:\n")
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+
+	domain := flag.Arg(0)
+	checkSet := types.ParseChecks(*checksFlag)
+
+	// Resolve the domain once so all checkers share the same IPs.
+	resolvedIPs, _ := net.LookupHost(domain)
+
+	result := types.AuditResult{
+		Domain: domain,
+		Time:   time.Now(),
+	}
+
+	if checkSet&types.CheckSSL != 0 {
+		result.SSL = ssl.Run(domain)
+	}
+	if checkSet&types.CheckHTTP != 0 {
+		result.HTTP = httpcheck.Run(domain)
+	}
+	if checkSet&types.CheckDNS != 0 {
+		result.DNS = dns.Run(domain)
+	}
+	if checkSet&types.CheckInfra != 0 {
+		result.Infra = infra.Run(domain, resolvedIPs)
+	}
+
+	// Determine output writer
+	var w = os.Stdout
+	if *outFlag != "" {
+		f, err := os.Create(*outFlag)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "error: cannot create output file: %v\n", err)
+			os.Exit(1)
+		}
+		defer f.Close()
+		w = f
+	}
+
+	if *jsonFlag {
+		report.JSON(w, result)
+	} else {
+		report.Terminal(w, result)
+	}
+}
+