feat: indicateur versioning sur cartes + toolbar éditeur

Note card:
- Icône History en overlay bottom-right (visible si historyEnabled=true)
- Discrète: text-muted-foreground/50, ne pollue pas l'UI
- Tooltip 'Historique des versions activé'

Toolbar éditeur:
- Icône History à côté du statut Saved/Dirty
- Visible seulement en sm+ (desktop)
- cursor-help + tooltip

i18n:
- notes.historyEnabledTooltip ajouté aux 15 locales (FR/EN traduits, 13 EN placeholder)

memento-note/components/note-card.tsx

@@ -24,7 +24,7 @@ import {
   AlertDialogHeader,
   AlertDialogTitle,
 } from '@/components/ui/alert-dialog'
-import { Pin, Bell, GripVertical, X, Link2, FolderOpen, StickyNote, LucideIcon, Folder, Briefcase, FileText, Zap, BarChart3, Globe, Sparkles, Book, Heart, Crown, Music, Building2, LogOut, Trash2, AlignLeft, FileCode2, PenLine, ListChecks, ChevronRight, Plus } from 'lucide-react'
+import { Pin, Bell, GripVertical, X, Link2, FolderOpen, StickyNote, LucideIcon, Folder, Briefcase, FileText, Zap, BarChart3, Globe, Sparkles, Book, Heart, Crown, Music, Building2, LogOut, Trash2, AlignLeft, FileCode2, PenLine, ListChecks, ChevronRight, Plus, History } from 'lucide-react'
 import { useState, useEffect, useTransition, useOptimistic, memo, useMemo } from 'react'
 import dynamic from 'next/dynamic'
 import { useSession } from 'next-auth/react'
@@ -594,6 +594,16 @@ export const NoteCard = memo(function NoteCard({
         />
       )}
 
+      {/* Versioning indicator */}
+      {optimisticNote.historyEnabled && (
+        <div
+          className="absolute bottom-3 end-3 z-10"
+          title={t('notes.historyEnabledTooltip') || 'Version history enabled'}
+        >
+          <History className="h-3.5 w-3.5 text-muted-foreground/50" />
+        </div>
+      )}
+
       {/* Fusion Badge */}
       {note.aiProvider === 'fusion' && optimisticNote.autoGenerated !== null && (
         <div className="px-1.5 py-0.5 rounded text-[10px] font-medium bg-purple-100 dark:bg-purple-900/30 text-purple-700 dark:text-purple-400 border border-purple-200 dark:border-purple-800 flex items-center gap-1 group/badge relative mb-2 w-fit">

memento-note/components/note-editor/note-editor-toolbar.tsx

@@ -19,7 +19,7 @@ import { Badge } from '@/components/ui/badge'
 import {
   X, Plus, Palette, Image as ImageIcon, Bell, Eye, Link as LinkIcon, Sparkles,
   Maximize2, Copy, ArrowLeft, ChevronRight, PanelRight, Check, Loader2, Save, MoreHorizontal,
-  Trash2, LogOut, Wand2, Share2, Wind, Paperclip, GraduationCap, FileDown, FileUp, Mic, MicOff, Printer, PenTool, Loader2 as Loader2Icon, Globe, ExternalLink
+  Trash2, LogOut, Wand2, Share2, Wind, Paperclip, GraduationCap, FileDown, FileUp, Mic, MicOff, Printer, PenTool, Loader2 as Loader2Icon, Globe, ExternalLink, History
 } from 'lucide-react'
 import { FlashcardGenerateDialog } from '@/components/flashcards/flashcard-generate-dialog'
 import { NoteShareDialog } from './note-share-dialog'
@@ -549,6 +549,15 @@ export function NoteEditorToolbar({ mode, onClose, onToggleAttachments, attachme
               : <><Check className="h-3 w-3 text-emerald-500" /><span>{t('notes.savedStatus')}</span></>}
           </span>
 
+          {note.historyEnabled && (
+            <span
+              className="hidden sm:flex items-center gap-1 text-[11px] text-foreground/35 select-none cursor-help"
+              title={t('notes.historyEnabledTooltip') || 'Version history enabled'}
+            >
+              <History className="h-3 w-3" />
+            </span>
+          )}
+
           {state.isMarkdown && !readOnly && (
             <button
               title={state.showMarkdownPreview ? t('notes.markdownEditingTitle') : t('notes.markdownPreviewTitle')}