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">