feat: add custom domain support with SSL, DNS verification, and billing

Users can assign a custom domain to their app with automatic SSL via
cert-manager. Includes DNS verification flow (CNAME check), Persian
instructions, admin-configurable pricing via PlatformSetting, and
integration into the deploy wizard cost calculation.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/common/enums.ts

@@ -90,6 +90,7 @@ export enum PricingResourceType {
   REDIS_ADDON = 'redis_addon',     // Price for Redis addon
   RABBITMQ_ADDON = 'rabbitmq_addon', // Price for RabbitMQ addon
   ELASTICSEARCH_ADDON = 'elasticsearch_addon', // Price for Elasticsearch addon
+  CUSTOM_DOMAIN_ADDON = 'custom_domain_addon', // Price for custom domain with SSL
 }
 
 export enum TransactionType {
@@ -98,6 +99,14 @@ export enum TransactionType {
   REFUND = 'refund',       // Refund
 }
 
+// ── Custom Domain ────────────────────────────────────
+
+export enum CustomDomainStatus {
+  NONE = 'none',
+  PENDING_DNS = 'pending_dns',
+  VERIFIED = 'verified',
+}
+
 // ── Application Lifecycle ─────────────────────────────
 
 export enum AppLifecycleStatus {