fix(routing-rules): backend selector showed (undefined:undefined) instead of scheme

The Backend interface declared address/port fields that don't exist on the
Backend model (those belong to BackendServer). The table column and the
backend select dropdown both rendered "name (undefined:undefined)". Fixed
by replacing phantom fields with scheme, matching the same fix applied to
Domains pages in v1.1.121.

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

management-ui/src/pages/RoutingRules/index.tsx

@@ -32,7 +32,7 @@ interface RuleFormValues {
 }
 
 interface Domain { id: number; name: string }
-interface Backend { id: number; name: string; address: string; port: number }
+interface Backend { id: number; name: string; scheme: string }
 
 async function listRules(): Promise<RoutingRule[]> {
   const r = await apiClient.get('/routing-rules')
@@ -83,7 +83,7 @@ export default function RoutingRulesPage() {
   const domainName = (id: number) => domains?.find((d) => d.id === id)?.name ?? `#${id}`
   const backendLabel = (id: number) => {
     const b = backends?.find((x) => x.id === id)
-    return b ? `${b.name} (${b.address}:${b.port})` : `#${id}`
+    return b ? `${b.name} (${b.scheme})` : `#${id}`
   }
   const backendHealth = (id: number) => {
     if (!haproxyStats?.length) return null
@@ -290,7 +290,7 @@ export default function RoutingRulesPage() {
           </Form.Item>
           <Form.Item label={t('routing.backend')} name="backend_id" rules={[{ required: true }]}>
             <Select
-              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})` }))}
               placeholder={t('routing.selectBackend')}
             />
           </Form.Item>