支持客服入口按业务场景分流到客服分组

联系客服支持 scene（general/mohong），按用户与场景复用会话；摸大红入口走摸大红分组选人。

frontend/src/layouts/AppLayout.vue

@@ -24,7 +24,7 @@ import {
   VideoPlay,
   Wallet,
 } from '@element-plus/icons-vue'
-import { ensureSupportChat } from '@/features/chats/api/chats'
+import { ensureSupportChat, resolveSupportScene } from '@/features/chats/api/chats'
 import { useChatUnreadCount } from '@/features/chats/composables/useChatUnreadCount'
 import { useSessionStore } from '@/stores/session'
 
@@ -111,7 +111,8 @@ async function handleSupportClick() {
   if (supportLoading.value) return
   supportLoading.value = true
   try {
-    const chat = await ensureSupportChat()
+    const scene = resolveSupportScene(route.path)
+    const chat = await ensureSupportChat(scene)
     router.push(`/messages/${chat.id}`)
   } catch {
     ElMessage.error('联系客服失败，请稍后重试')