fix: Fix box-sizing of Layout Editor - MEED-6806 - Meeds-io/meeds#1966

Prior to this change, the Layout editor wasn't displaying the right proportions when moving applications. This is due to the inherited box sizing which changed by the introduction of singlePageApplication.

layout-webapp/src/main/webapp/vue-app/layout-editor/components/LayoutEditor.vue

@@ -23,7 +23,7 @@
     class="transparent"
     role="main"
     flat>
-    <div>
+    <div class="content-box-sizing">
       <layout-editor-toolbar
         :disable-save="!modified"
         :page="pageContext"

layout-webapp/src/main/webapp/vue-app/layout-editor/components/content/base/CellsDropBox.vue

@@ -22,7 +22,7 @@
   <div
     ref="movingBox"
     :style="boxStyle"
-    class="layout-selecting-container d-flex position-absolute elevation-2 z-index-modal">
+    class="layout-selecting-container border-box-sizing d-flex position-absolute elevation-2 z-index-modal">
   </div>
 </template>
 <script>

layout-webapp/src/main/webapp/vue-app/layout-editor/components/content/base/CellsSelectionBox.vue

@@ -22,7 +22,7 @@
   <div
     v-show="multiCellsSelect"
     :style="boxStyle"
-    class="layout-selecting-container grey opacity-5 elevation-2 position-absolute z-index-modal">
+    class="layout-selecting-container border-box-sizing grey opacity-5 elevation-2 position-absolute z-index-modal">
   </div>
 </template>
 <script>

layout-webapp/src/main/webapp/vue-app/layout-editor/components/content/common/SectionSelectionGrid.vue

@@ -19,7 +19,7 @@
 
 -->
 <template>
-  <div :class="gridClass">
+  <div :class="gridClass" class="border-box-sizing pb-5">
     <layout-editor-section-selection-grid-cell
       v-for="i in length"
       :id="`grid-cell-${i}`"

layout-webapp/src/main/webapp/vue-app/layout-editor/components/content/container/Cell.vue

@@ -27,7 +27,6 @@
     :hide-children="moving"
     :class="{
       'z-index-two': hover && !$root.drawerOpened,
-      'pb-12': movingChildren,
     }"
     :style="cssStyle"
     class="position-relative d-flex flex-column"