Add catalog-zone-gen tool

Generate RFC 9432 DNS catalog zone files from a declarative input file.
Parses zone-to-catalog assignments with optional group and coo properties,
produces deterministic BIND-format output with automatic SOA serial
management and change detection.

main.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"time"
+)
+
+func main() {
+	configPath := flag.String("config", "", "path to YAML config (default: catz.yaml next to input file)")
+	outputDir := flag.String("output-dir", "", "directory for output zone files (default: same as input file)")
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: catalog-zone-gen [--config path] [--output-dir path] <input-file>\n")
+		flag.PrintDefaults()
+	}
+	flag.Parse()
+
+	if flag.NArg() != 1 {
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	inputFile := flag.Arg(0)
+	inputDir := filepath.Dir(inputFile)
+
+	if *configPath == "" {
+		*configPath = filepath.Join(inputDir, "catz.yaml")
+	}
+	if *outputDir == "" {
+		*outputDir = inputDir
+	}
+
+	cfg, err := loadConfig(*configPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error: %s\n", err)
+		os.Exit(1)
+	}
+
+	members, err := parseInput(inputFile, cfg)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n", err)
+		os.Exit(1)
+	}
+
+	now := time.Now().UTC()
+
+	// Process catalogs in sorted order for deterministic output
+	catNames := make([]string, 0, len(members))
+	for name := range members {
+		catNames = append(catNames, name)
+	}
+	sort.Strings(catNames)
+
+	hasErrors := false
+	for _, catName := range catNames {
+		changed, err := processCatalog(catName, cfg, members[catName], *outputDir, now)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%s\n", err)
+			hasErrors = true
+			continue
+		}
+		catZone := cfg.Catalogs[catName].Zone
+		if changed {
+			fmt.Fprintf(os.Stderr, "%s%s: updated\n", catZone, "zone")
+		} else {
+			fmt.Fprintf(os.Stderr, "%s%s: unchanged\n", catZone, "zone")
+		}
+	}
+
+	if hasErrors {
+		os.Exit(1)
+	}
+}