fix(domains): backend column showed (undefined:undefined) instead of scheme

BackendLite interfaces in Domains list and Detail declared address/port
fields that don't exist on the Backend model (those live on BackendServer).
Every backend tag rendered as "name (undefined:undefined)". Fixed by
replacing the phantom fields with scheme, so tags show e.g. "my-app (https)".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

management-ui/src/pages/Domains/Detail.tsx

@@ -56,7 +56,7 @@ interface RoutingRule {
   backend_id: number; priority: number; active: boolean
 }
 
-interface BackendLiteWithAddr { id: number; name: string; address: string; port: number }
+interface BackendLiteWithAddr { id: number; name: string; scheme: string }
 
 interface TLSCertLite {
   domain: string
@@ -426,7 +426,7 @@ function RoutingRulesPanel({ domainID, domainName, isViewer }: { domainID: numbe
 
   const backendLabel = (id: number) => {
     const b = backends?.find(x => x.id === id)
-    return b ? `${b.name} (${b.address}:${b.port})` : `#${id}`
+    return b ? `${b.name} (${b.scheme})` : `#${id}`
   }
 
   const columns: ColumnsType<RoutingRule> = [
@@ -523,7 +523,7 @@ function RoutingRulesPanel({ domainID, domainName, isViewer }: { domainID: numbe
             <Select
               showSearch optionFilterProp="label"
               placeholder={t('routing.selectBackend')}
-              options={(backends ?? []).map(b => ({ value: b.id, label: `${b.name} (${b.address}:${b.port})` }))}
+              options={(backends ?? []).map(b => ({ value: b.id, label: `${b.name} (${b.scheme})` }))}
             />
           </Form.Item>
           <Form.Item label={t('routing.priority')} name="priority" rules={[{ required: true }]}>