调整 api 目录，代码优化

src/views/dashboard/LineChart.vue

@@ -6,7 +6,7 @@
 import echarts from 'echarts'
 require('echarts/theme/macarons') // echarts theme
 import { debounce } from '@/utils'
-import { getChartData } from '@/api/visits'
+import { getChartData } from '@/api/monitor/visits'
 
 export default {
   props: {

src/views/dashboard/PanelGroup.vue

@@ -49,7 +49,7 @@
 
 <script>
 import CountTo from 'vue-count-to'
-import { get } from '@/api/visits'
+import { get } from '@/api/monitor/visits'
 export default {
   components: {
     CountTo