/login -> /signin 변경

frontend/lib/features/auth/presentation/approve_qr_screen.dart

@@ -22,7 +22,7 @@ class _ApproveQrScreenState extends State<ApproveQrScreen> {
     final session = Descope.sessionManager.session;
     if (session == null || session.refreshToken.isExpired) {
       setState(() => _message = "Please log in on your phone first.");
-      context.go('/login'); // Redirect to login
+      context.go('/signin'); // Redirect to login
       return;
     }
 
@@ -103,7 +103,7 @@ class _ApproveQrScreenState extends State<ApproveQrScreen> {
                 Padding(
                   padding: const EdgeInsets.only(top: 16),
                   child: TextButton(
-                    onPressed: () => context.go('/login'),
+                    onPressed: () => context.go('/signin'),
                     child: const Text("Login on this device first"),
                   ),
                 ),