Improve link styling and accessibility in the sidebar navigation

Refactor Link components in sidebar.tsx to use the new Next.js 13+ App Router syntax, removing unnecessary `<a>` tags and simplifying className application.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: ae4037a0-2a6f-4530-9bac-79b543286bda
Replit-Commit-Checkpoint-Type: intermediate_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/397bca8c-984f-43ff-841a-10897aeb8140/ae4037a0-2a6f-4530-9bac-79b543286bda/ds3R7vP

client/src/components/sidebar.tsx

@@ -40,8 +40,8 @@ export default function Sidebar() {
             
             return (
               <li key={item.href}>
-                <Link href={item.href}>
+                <Link 
-                  <a 
+                  href={item.href}
                   className={`
                     flex items-center gap-3 px-4 py-3 rounded-lg font-medium transition-all
                     ${isActive 
@@ -58,7 +58,6 @@ export default function Sidebar() {
                       {item.badge}
                     </span>
                   )}
-                  </a>
                 </Link>
               </li>
             );
@@ -74,8 +73,8 @@ export default function Sidebar() {
               
               return (
                 <li key={item.href}>
-                  <Link href={item.href}>
+                  <Link 
-                    <a 
+                    href={item.href}
                     className={`
                       flex items-center gap-3 px-4 py-3 rounded-lg transition-all
                       ${isActive 
@@ -87,7 +86,6 @@ export default function Sidebar() {
                   >
                     <Icon className="w-5 h-5" />
                     <span>{item.label}</span>
-                    </a>
                   </Link>
                 </li>
               );
@@ -97,14 +95,13 @@ export default function Sidebar() {
       </nav>
 
       <div className="p-4 border-t border-border">
-        <Link href="/settings">
+        <Link 
-          <a 
+          href="/settings"
           className="flex items-center gap-3 px-4 py-3 rounded-lg text-muted-foreground hover:bg-accent hover:text-accent-foreground transition-all"
           data-testid="link-settings"
         >
           <Settings className="w-5 h-5" />
           <span>Paramètres</span>
-          </a>
         </Link>
       </div>
     </aside>