feat(splash): route to device setup when a logged-in user has zero devices

Extend CheckSessionUseCase to fetch /devices after confirming the
session and return InitialRoute.deviceSetup when the list is empty
(or the call fails). The splash builder now injects a
SharedDevicesRepository alongside the user repository, and the app
router maps the new route to legacyDeviceSetup / deviceSetup per
shell. The legacy builder reads legacyDevicesProvider to derive
isFirstDevice so the setup screen adapts its copy accordingly.

apps/mobile_app/lib/navigation/app_router.dart

@@ -51,12 +51,14 @@ const _legacySplashRouteMap = <InitialRoute, String>{
   InitialRoute.onboarding: AppRoutes.legacyOnboarding,
   InitialRoute.login: AppRoutes.legacyLogin,
   InitialRoute.home: AppRoutes.controlPanel,
+  InitialRoute.deviceSetup: AppRoutes.legacyDeviceSetup,
 };
 
 const _paymentSplashRouteMap = <InitialRoute, String>{
   InitialRoute.onboarding: AppRoutes.onboarding,
   InitialRoute.login: AppRoutes.login,
   InitialRoute.home: AppRoutes.dashboardHome,
+  InitialRoute.deviceSetup: AppRoutes.deviceSetup,
 };
 
 void configureAppRouter() {

modules/legacy/modules/legacy_auth/lib/src/features/device_setup/device_setup_builder.dart

@@ -1,18 +1,28 @@
 import 'package:legacy_auth/src/features/device_setup/presentation/device_setup_screen.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:get_it/get_it.dart';
 import 'package:go_router/go_router.dart';
 import 'package:navigation/navigation.dart';
+import 'package:sf_shared/sf_shared.dart';
 
 class LegacyDeviceSetupBuilder {
   const LegacyDeviceSetupBuilder();
 
   Page<void> buildPage(BuildContext context, GoRouterState state) {
-    final NavigationContract navigationContract = GetIt.I<NavigationContract>();
+    final navigationContract = GetIt.I<NavigationContract>();
 
     return MaterialPage<void>(
       key: state.pageKey,
-      child: LegacyDeviceSetupScreen(navigationContract: navigationContract),
+      child: Consumer(
+        builder: (context, ref, _) {
+          final devices = ref.watch(legacyDevicesProvider).value ?? [];
+          return LegacyDeviceSetupScreen(
+            navigationContract: navigationContract,
+            isFirstDevice: devices.isEmpty,
+          );
+        },
+      ),
     );
   }
 }

modules/splash/lib/src/domain/check_session_use_case_impl.dart

@@ -6,11 +6,12 @@ import 'check_session_use_case.dart';
 import 'initial_route.dart';
 
 class CheckSessionUseCaseImpl implements CheckSessionUseCase {
-  CheckSessionUseCaseImpl(this._userRepository);
+  CheckSessionUseCaseImpl(this._userRepository, this._devicesRepository);
 
   static const _onboardingSeenKey = 'onboarding_seen';
 
   final UserRepository _userRepository;
+  final SharedDevicesRepository _devicesRepository;
 
   @override
   Future<InitialRoute> execute() async {
@@ -26,10 +27,23 @@ class CheckSessionUseCaseImpl implements CheckSessionUseCase {
 
     try {
       await _userRepository.getUserInfo();
-      return InitialRoute.home;
     } catch (e) {
-      debugPrint('[CheckSessionUseCase] error: $e');
+      debugPrint('[CheckSession] no session: $e');
       return InitialRoute.login;
     }
+
+    try {
+      final devices = await _devicesRepository.getDevices();
+      if (devices.isEmpty) {
+        debugPrint('[CheckSession] → deviceSetup (0 devices)');
+        return InitialRoute.deviceSetup;
+      }
+    } catch (e) {
+      debugPrint('[CheckSession] devices check failed: $e');
+      return InitialRoute.deviceSetup;
+    }
+
+    debugPrint('[CheckSession] → home');
+    return InitialRoute.home;
   }
 }

modules/splash/lib/src/domain/initial_route.dart

@@ -1 +1 @@
-enum InitialRoute { login, home, onboarding }
+enum InitialRoute { login, home, onboarding, deviceSetup }

modules/splash/lib/src/splash_builder.dart

@@ -18,9 +18,10 @@ class SplashBuilder {
 
   Page<void> buildPage(BuildContext context, GoRouterState state) {
     final navigationContract = GetIt.I<NavigationContract>();
-    final remote = UserRemoteDatasourceImpl(GetIt.I<SaveFamilyRepository>());
-    final userRepository = UserRepositoryImpl(remote);
-    final checkSessionUseCase = CheckSessionUseCaseImpl(userRepository);
+    final repository = GetIt.I<SaveFamilyRepository>();
+    final userRepository = UserRepositoryImpl(UserRemoteDatasourceImpl(repository));
+    final devicesRepository = DevicesRepositoryImpl(DevicesRemoteDatasourceImpl(repository));
+    final checkSessionUseCase = CheckSessionUseCaseImpl(userRepository, devicesRepository);
 
     return NoTransitionPage(
       child: SplashScreen(