fix: redirect to /briefing after auth (was /notes which no longer exists)

lib/screens/auth/login_screen.dart

@@ -72,7 +72,7 @@ class _LoginScreenState extends ConsumerState<LoginScreen> {
             _usernameController.text.trim(),
             _passwordController.text,
           );
-      if (mounted) context.go(Routes.notes);
+      if (mounted) context.go(Routes.briefing);
     } on AuthException catch (e) {
       setState(() => _error = e.message);
     } on AppException catch (e) {
@@ -90,7 +90,7 @@ class _LoginScreenState extends ConsumerState<LoginScreen> {
         cookieJar: ref.read(cookieJarProvider),
         onSuccess: () async {
           await ref.read(authProvider.notifier).verify();
-          if (mounted) context.go(Routes.notes);
+          if (mounted) context.go(Routes.briefing);
         },
       ),
     ));

lib/screens/splash/splash_screen.dart

@@ -30,7 +30,7 @@ class _SplashScreenState extends ConsumerState<SplashScreen> {
     if (!mounted) return;
     final status = ref.read(authProvider);
     if (status == AuthStatus.authenticated) {
-      context.go(Routes.notes);
+      context.go(Routes.briefing);
     } else {
       context.go(Routes.login);
     }