refactor(auth): replace anchor tags with fullghost Button variant for navigation links

src/features/auth/pages/ForgotPasswordPage.client.js

@@ -117,17 +117,15 @@ export default function ForgotPasswordPage({ onSubmit, onNavigate, currentUser =
         </Button>
       </form>
 
-      <div className={`mt-6 text-center transition-opacity duration-200 ${currentUser ? 'opacity-50 pointer-events-none' : ''}`}>
-        <a
-          href="#"
-          onClick={(e) => {
-            e.preventDefault();
-            if (!currentUser) onNavigate('login');
-          }}
-          className="text-sm text-neutral-900 hover:text-neutral-600 font-medium transition-colors duration-200 dark:text-white dark:hover:text-neutral-300"
+      <div className={`mt-6 flex justify-center transition-opacity duration-200 ${currentUser ? 'opacity-50 pointer-events-none' : ''}`}>
+        <Button
+          type="button"
+          variant="fullghost"
+          disabled={!!currentUser}
+          onClick={() => { if (!currentUser) onNavigate('login'); }}
         >
           ← Retour à la connexion
-        </a>
+        </Button>
       </div>
     </Card>
   );

src/features/auth/pages/LoginPage.client.js

@@ -164,7 +164,7 @@ export default function LoginPage({ onSubmit, onNavigate, onSetSessionCookie, re
       <div className={`mt-6 flex justify-center transition-opacity duration-200 ${currentUser ? 'opacity-50 pointer-events-none' : ''}`}>
         <Button
           type="button"
-          variant="ghost"
+          variant="fullghost"
           disabled={!!currentUser}
           onClick={() => { if (!currentUser) onNavigate('register'); }}
         >

src/features/auth/pages/RegisterPage.client.js

@@ -220,7 +220,7 @@ export default function RegisterPage({ onSubmit, onNavigate, currentUser = null
       <div className={`mt-6 flex justify-center transition-opacity duration-200 ${currentUser ? 'opacity-50 pointer-events-none' : ''}`}>
         <Button
           type="button"
-          variant="ghost"
+          variant="fullghost"
           disabled={!!currentUser}
           onClick={() => { if (!currentUser) onNavigate('login'); }}
         >

src/features/auth/pages/ResetPasswordPage.client.js

@@ -138,14 +138,14 @@ export default function ResetPasswordPage({ onSubmit, onNavigate, email, token }
         </Button>
       </form>
 
-      <div className="mt-6 text-center">
-        <a
-          href="#"
-          onClick={(e) => { e.preventDefault(); onNavigate('login'); }}
-          className="text-sm text-neutral-900 hover:text-neutral-600 font-medium transition-colors duration-200 dark:text-white dark:hover:text-neutral-300"
+      <div className="mt-6 flex justify-center">
+        <Button
+          type="button"
+          variant="fullghost"
+          onClick={() => onNavigate('login')}
         >
           ← Retour à la connexion
-        </a>
+        </Button>
       </div>
     </Card>
   );