fix(frontend): serve zone detail static export fallback

internal/router/root/frontend_static.go

@@ -0,0 +1,34 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package root
+
+import (
+	"io/fs"
+	"strings"
+)
+
+//nolint:unused // Used by frontend.go in embed_frontend builds; default lint runs without that tag.
+func resolveNextExportDynamicFallback(subFS fs.FS, cleanPath string) (string, bool) {
+	parts := strings.Split(cleanPath, "/")
+	if len(parts) < 2 || parts[0] != "websites" || parts[1] == "" {
+		return "", false
+	}
+
+	var templatePath string
+	switch {
+	case len(parts) == 2 && !strings.Contains(parts[1], "."):
+		templatePath = "websites/1.html"
+	case len(parts) == 2 && strings.HasSuffix(parts[1], ".txt"):
+		templatePath = "websites/1.txt"
+	case len(parts) == 3 && parts[2] != "" && strings.HasPrefix(parts[2], "__next.") && strings.HasSuffix(parts[2], ".txt"):
+		templatePath = "websites/1/" + parts[2]
+	default:
+		return "", false
+	}
+
+	if _, err := fs.Stat(subFS, templatePath); err != nil {
+		return "", false
+	}
+	return templatePath, true
+}