perf: 优化区域管理页面性能

- 使用后端 /region/tree 接口，避免前端递归构建树
- 默认折叠树节点，减少 DOM 渲染

frontend/ruoyi-ui/src/views/business/base/region/index.vue

@@ -118,7 +118,7 @@ const loading = ref(false)
 const tableData = ref([])
 const regionOptions = ref([])
 const refreshTable = ref(true)
-const isExpandAll = ref(true)
+const isExpandAll = ref(false) // 默认折叠，避免渲染大量节点
 
 const queryParams = ref({
   regionName: '',
@@ -141,13 +141,13 @@ const rules = {
   regionName: [{ required: true, message: '请输入区域名称', trigger: 'blur' }]
 }
 
-// 获取区域列表（树形）
+// 获取区域列表（树形）- 使用后端已构建好的树接口
 const getList = async () => {
   loading.value = true
   try {
-    const res = await request.get('/business/region/list', { params: queryParams.value })
+    const res = await request.get('/business/region/tree')
     if (res.code === 200) {
-      tableData.value = buildTree(res.data || [])
+      tableData.value = res.data || []
     }
   } finally {
     loading.value = false
@@ -156,23 +156,12 @@ const getList = async () => {
 
 // 获取区域树选项（用于下拉选择）
 const getRegionOptions = async () => {
-  const res = await request.get('/business/region/list')
+  const res = await request.get('/business/region/tree')
   if (res.code === 200) {
-    regionOptions.value = [{ regionId: 0, regionName: '顶级区域', children: buildTree(res.data || []) }]
+    regionOptions.value = [{ regionId: 0, regionName: '顶级区域', children: res.data || [] }]
   }
 }
 
-// 构建树形结构
-const buildTree = (data, parentId = 0) => {
-  return data
-    .filter(item => item.parentId === parentId)
-    .map(item => ({
-      ...item,
-      children: buildTree(data, item.regionId)
-    }))
-    .filter(item => item.children.length > 0 || data.some(d => d.regionId === item.regionId))
-}
-
 // 展开/折叠
 const toggleExpandAll = () => {
   refreshTable.value = false