fix: login → SuperOAuth root page (redirectUrl), drop LoginPage interne

frontend/src/components/layout/Header.tsx

@@ -10,6 +10,8 @@ interface HeaderProps {
 }
 
 export default function Header({ theme, onToggleTheme, user, onLogout }: HeaderProps) {
+  const loginUrl = `${import.meta.env.VITE_SUPEROAUTH_URL}?redirectUrl=${encodeURIComponent(window.location.origin + '/callback')}`;
+
   async function handleLogout() {
     await apiFetch('/auth/logout', { method: 'POST' }).catch(() => {});
     onLogout();
@@ -62,12 +64,12 @@ export default function Header({ theme, onToggleTheme, user, onLogout }: HeaderP
               </button>
             </div>
           ) : (
-            <Link
-              to="/login"
+            <a
+              href={loginUrl}
               className="rounded border border-od-border px-3 py-1 font-mono text-xs text-od-muted hover:border-od-accent hover:text-od-accent transition-colors"
             >
               Connexion
-            </Link>
+            </a>
           )}
         </div>