fix: arbre collapse après drag-drop (expanded persistant via localStorage)

Avant: tout window.location.reload() réinitialisait expanded={},
causant le collapse de tous les dossiers après un drop.

Fix:
- expanded initialisé depuis localStorage('fd_ws_expanded')
- _saveExpandedState() sauve avant toute navigation/reload
- _reloadAfterAction() = save + reload
- toggleExpand, navigateToFolder, expandAll sauvent l'état
- Tous les reload (create, rename, delete, move, upload) passent par _reloadAfterAction()

app/templates/local_workspace.html

@@ -300,7 +300,10 @@ document.addEventListener('alpine:init', function() {
     newName:'',
     parentFolder:null,
     target:null,
-    expanded: {},
+    expanded: (function() {
+      try { return JSON.parse(localStorage.getItem('fd_ws_expanded') || '{}'); }
+      catch(e) { return {}; }
+    })(),
     currentFolder: {{ current_folder_id }},
     searchQuery: '',
 
@@ -429,6 +432,7 @@ document.addEventListener('alpine:init', function() {
     toggleExpand(id, btn) {
       this.expanded[id] = !(this.expanded[id] || false);
       this.expanded = Object.assign({}, this.expanded);
+      this._saveExpandedState();
       // For renderChildren static HTML: toggle chevron + sibling <ul>
       if (btn) {
         btn.classList.toggle('open', this.expanded[id]);
@@ -447,9 +451,19 @@ document.addEventListener('alpine:init', function() {
     },
 
     navigateToFolder(id) {
+      this._saveExpandedState();
       window.location = '/local-workspace?folder=' + id;
     },
 
+    _saveExpandedState() {
+      try { localStorage.setItem('fd_ws_expanded', JSON.stringify(this.expanded)); }
+      catch(e) {}
+    },
+    _reloadAfterAction() {
+      this._saveExpandedState();
+      this._reloadAfterAction();
+    },
+
     // ── Expand / Collapse all ──
     expandAll() {
       var self = this;
@@ -597,7 +611,7 @@ document.addEventListener('alpine:init', function() {
         this.showCreate = false;
         this.parentFolder = null;
         this.newName = '';
-        window.location.reload();
+        this._reloadAfterAction();
       }
     },
 
@@ -622,7 +636,7 @@ document.addEventListener('alpine:init', function() {
         headers:{'Content-Type':'application/json'},
         body:JSON.stringify({name:n})
       });
-      if (r.ok) { window.location.reload(); }
+      if (r.ok) { this._reloadAfterAction(); }
     },
 
     startDelete(node) {
@@ -633,7 +647,7 @@ document.addEventListener('alpine:init', function() {
     async doDelete() {
       if (!this.target) return;
       var r = await fetch('/api/local-workspace/items/'+this.target.db_id, { method:'DELETE' });
-      if (r.ok) { window.location.reload(); }
+      if (r.ok) { this._reloadAfterAction(); }
     },
 
     // ── Drag & Drop ──
@@ -829,7 +843,7 @@ document.addEventListener('alpine:init', function() {
           body: JSON.stringify(body)
         });
         if (r.ok) {
-          window.location.reload();
+          this._reloadAfterAction();
         } else {
           alert('Move failed');
         }
@@ -857,7 +871,7 @@ document.addEventListener('alpine:init', function() {
           var items = d.items || [];
           setTimeout(function() {
             self.uploading = false;
-            window.location.reload();
+            this._reloadAfterAction();
           }, 800);
         } else {
           this.uploadStatus = '✗ ' + (d.error || 'Upload failed');