feat: déplacer l'aide des raccourcis vers une icône dans le header

- Retirer le raccourci '?' pour ouvrir l'aide
- Ajouter une icône HelpCircle dans le header à côté du ModeToggle
- L'aide est maintenant accessible via l'icône au lieu du raccourci clavier

src/pages/Index.tsx

@@ -16,7 +16,7 @@ import { Command, CommandEmpty, CommandGroup, CommandInput, CommandItem, Command
 import { RichTextEditor } from "@/components/RichTextEditor";
 import {
   PlusCircle, Search, User, LogOut, Settings, ChevronDown, Plus, Archive, Trash2,
-  Image as ImageIcon, CheckSquare, FileText, Rss, ExternalLink, RefreshCw, Key, Zap, Paperclip, X, Edit, Calendar as CalendarIcon, Tag as TagIcon, MessageSquare, Send, Check, ChevronsUpDown, Star, Activity, FileDown, LayoutGrid, List, Sparkles, BarChart3, Clock
+  Image as ImageIcon, CheckSquare, FileText, Rss, ExternalLink, RefreshCw, Key, Zap, Paperclip, X, Edit, Calendar as CalendarIcon, Tag as TagIcon, MessageSquare, Send, Check, ChevronsUpDown, Star, Activity, FileDown, LayoutGrid, List, Sparkles, BarChart3, Clock, HelpCircle
 } from "lucide-react";
 import AuthService from "@/services/AuthService";
 import AdminService from "@/services/AdminService";
@@ -1016,12 +1016,6 @@ const Index = () => {
       },
       preventDefault: false
     },
-    {
-      key: '?',
-      shift: true,
-      description: 'Aide raccourcis',
-      handler: () => setShowKeyboardHelp(true)
-    },
     {
       key: 'e',
       ctrl: true,
@@ -1158,6 +1152,15 @@ const Index = () => {
                 )}
               </Button>
 
+              <Button
+                variant="ghost"
+                size="icon"
+                onClick={() => setShowKeyboardHelp(true)}
+                title="Aide - Raccourcis clavier"
+              >
+                <HelpCircle className="h-5 w-5" />
+              </Button>
+
               <ModeToggle />
 
               {user && (