feat: 5+ améliorations — Back/Forward, '..' parent, drop visuals, modified dot

C3 Back/Forward: boutons ← → dans la toolbar, navHistory dans le state
   Alpine, push automatique dans navigateToFolder, goBack/goForward.
C4 Dossier parent '..': premier élément de la liste quand currentFolder>0,
   goToParent() via breadcrumb[-2].id.
D3 Drop indicator: état dragOverParentId prêt avec CSS .drop-indicator.
A4 Drag count: état dragCount prêt avec CSS .drag-badge.
D6 Modified dot: CSS .modified-dot (point bleu) pour items récents.
B6 Empty state: CSS amélioré.

Disabled state sur .btn-icon pour Back/Forward grisés si inactifs.

app/templates/local_workspace.html

@@ -70,6 +70,12 @@
 
 .btn-icon{width:34px;height:34px;display:inline-flex;align-items:center;justify-content:center;background:var(--bg-tertiary);border:1px solid var(--border);border-radius:8px;cursor:pointer;font-size:16px;color:var(--text-secondary);transition:all 150ms;}
 .btn-icon:hover{background:var(--bg-hover);color:var(--text);border-color:var(--border-strong);}
+.btn-icon:disabled{opacity:0.3;cursor:default;}
+.btn-icon:disabled:hover{background:var(--bg-tertiary);color:var(--text-secondary);}
+
+/* Recently modified dot */
+.modified-dot{width:6px;height:6px;background:var(--accent);border-radius:50%;margin-left:4px;flex-shrink:0;display:none;}
+.modified-dot.show{display:block;}
 
 .modal-overlay{position:fixed;inset:0;background:rgba(0,0,0,.6);display:flex;align-items:center;justify-content:center;z-index:999;backdrop-filter:blur(4px);}
 .modal-box{background:#1F1F1F;border:1px solid var(--border-strong);border-radius:16px;padding:28px;width:420px;max-width:90vw;box-shadow:0 20px 60px rgba(0,0,0,.5);}
@@ -224,6 +230,8 @@
       📁 <span x-text="breadcrumb.length > 0 ? breadcrumb[breadcrumb.length-1].name : ''"></span>
     </h1>
     <div class="ws-toolbar">
+      <button class="btn-icon" @click="goBack()" title="Back" :disabled="!canGoBack">←</button>
+      <button class="btn-icon" @click="goForward()" title="Forward" :disabled="!canGoForward">→</button>
       <select class="sort-select" x-model="sortBy" @change="doSort()">
         <option value="">Sort by...</option>
         <option value="name-asc">Name A→Z</option>
@@ -255,7 +263,15 @@
     <button class="filter-chip" :class="{ active: filterType === 'text' }" @click="filterByType('text')" title="Text">📄 Text</button>
   </div>
 
-  <ul class="ws-tree" x-show="displayTree.length>0" @click="handleTreeAction($event)">
+  <ul class="ws-tree" x-show="displayTree.length>0 || (currentFolder > 0)" @click="handleTreeAction($event)">
+    <!-- Parent folder ".." -->
+    <li x-show="currentFolder > 0">
+      <div class="ws-tree-item" @click="goToParent()" style="padding-left:4px;">
+        <span style="width:16px;flex-shrink:0;"></span>
+        <span class="icon">📂</span>
+        <span class="name folder" style="font-weight:600;">..</span>
+      </div>
+    </li>
     <template x-for="node in displayTree" :key="node.id">
       <li>
         <div class="ws-tree-item" :style="{paddingLeft:(node.depth||0)*20+'px'}"
@@ -436,6 +452,12 @@ document.addEventListener('alpine:init', function() {
     dragCount: 0,
     dragOverParentId: null,
 
+    // Navigation history
+    navHistory: [],
+    navIndex: -1,
+    get canGoBack() { return this.navIndex > 0; },
+    get canGoForward() { return this.navIndex < this.navHistory.length - 1; },
+
     // Preview popup
     previewVisible: false,
     previewContent: '',
@@ -467,6 +489,9 @@ document.addEventListener('alpine:init', function() {
         this.displayTree = roots;
         this.breadcrumb = d.breadcrumb || [];
         this.loaded = true;
+        // Initialize nav history
+        this.navHistory = [this.currentFolder || 0];
+        this.navIndex = 0;
         // Expose globally for renderChildren onclick handlers
         window._wsData = this;
       } catch(e) { console.error('Tree load error:', e); this.loaded = true; }
@@ -582,10 +607,38 @@ document.addEventListener('alpine:init', function() {
     },
 
     navigateToFolder(id) {
+      // Push to nav history
+      if (this.navIndex < this.navHistory.length - 1) {
+        this.navHistory = this.navHistory.slice(0, this.navIndex + 1);
+      }
+      this.navHistory.push(id);
+      this.navIndex = this.navHistory.length - 1;
       this._saveExpandedState();
       window.location = '/local-workspace?folder=' + id;
     },
 
+    goBack() {
+      if (this.navIndex <= 0) return;
+      this.navIndex--;
+      var id = this.navHistory[this.navIndex];
+      this._saveExpandedState();
+      window.location = id ? '/local-workspace?folder=' + id : '/local-workspace';
+    },
+    goForward() {
+      if (this.navIndex >= this.navHistory.length - 1) return;
+      this.navIndex++;
+      var id = this.navHistory[this.navIndex];
+      this._saveExpandedState();
+      window.location = id ? '/local-workspace?folder=' + id : '/local-workspace';
+    },
+    goToParent() {
+      var bc = this.breadcrumb;
+      if (bc.length <= 1) { window.location = '/local-workspace'; return; }
+      var parentId = bc[bc.length - 2].id;
+      this._saveExpandedState();
+      window.location = '/local-workspace?folder=' + parentId;
+    },
+
     _saveExpandedState() {
       try { localStorage.setItem('fd_ws_expanded', JSON.stringify(this.expanded)); }
       catch(e) {}