fix: var _wsInitData globale + anti-cache headers HTML

- x-data="_wsInitData" référence la variable globale JS (pas window.)
- var _wsInitData = IIFE — propriété window automatique pour compatibilité window._wsData
- Headers Cache-Control: no-cache, no-store, must-revalidate sur la page HTML
- 73 tests OK

app/templates/local_workspace.html

@@ -336,7 +336,7 @@
 .preview-leave-end{transform:translateX(100%);opacity:0;}
 </style>
 
-<div class="ws-split" x-data="window._wsInitData"
+<div class="ws-split" x-data="_wsInitData"
      @dragover.prevent="onDragOver($event)"
      @dragleave="onDragLeave($event)"
      @drop.prevent="onDrop($event)"
@@ -867,7 +867,7 @@
 </div><!-- /ws-split -->
 
 <script>
-window._wsInitData = (function() {
+var _wsInitData = (function() {
   return {
     tree:[],
     displayTree:[],