feat(dns): simplify PROD Route 53 by using prod-sacc.ccsoft.mx directly

Switch PROD DNS from cross-account Route 53 management to a delegated
subdomain in the PROD AWS account (523761210517).

Changes:
- prod.tfvars: domain_name changed to prod-sacc.ccsoft.mx
- provider.tf: removed aws.route53 cross-account provider
- main.tf: removed prod-specific Route 53 resources and data sources;
  cert_validation and main records now use default provider for all envs
- outputs.tf: removed indexed references to main_prod resource

terraform/outputs.tf

@@ -43,7 +43,7 @@ output "cloudfront_distribution_id" {
 
 output "route53_record" {
   description = "Registro DNS creado en Route 53"
-  value       = try(aws_route53_record.main[0].name, aws_route53_record.main_prod[0].name, "")
+  value       = aws_route53_record.main.name
 }
 
 output "acm_certificate_arn" {