fix(aiot): 修复时间选择器placeholder语法错误

- 将 placeholder 字符串改为数组绑定 :placeholder
- 修复 Vue 编译错误：Attribute name cannot contain quotes

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

apps/web-antd/src/views/aiot/device/roi/components/WorkingHoursEditor.vue

@@ -233,7 +233,7 @@ function getDuration(period: WorkingHourPeriod): string {
           v-model:value="currentRange"
           format="HH:mm"
           :minute-step="30"
-          placeholder="["开始时间", "结束时间"]"
+          :placeholder="['开始时间', '结束时间']"
           style="flex: 1"
         />
         <Button v-if="editingIndex !== null" @click="cancelEdit">