feat(frontend): simulate authenticated user sessions

eme-frontend/lib/screens/login_screen.dart

@@ -1,6 +1,7 @@
 import "package:flutter/material.dart";
 import "package:google_fonts/google_fonts.dart";
 import "../demo_identity.dart";
+import "../services/auth_service.dart";
 import "../theme/ensup_colors.dart";
 import "../widgets/ensup_top_bar.dart";
 import "../widgets/identification_option.dart";
@@ -13,6 +14,7 @@ class LoginScreen extends StatelessWidget {
   const LoginScreen({super.key});
 
   void _identifier(BuildContext context) {
+    AuthService.selectDemoStudent();
     Navigator.of(context).push(
       MaterialPageRoute(
         builder: (_) => const HomeScreen(),
@@ -21,6 +23,16 @@ class LoginScreen extends StatelessWidget {
     );
   }
 
+  void _identifierResponsable(BuildContext context) {
+    AuthService.selectDemoResponsable();
+    Navigator.of(context).push(
+      MaterialPageRoute(
+        builder: (_) => const ResponsableScreen(),
+        settings: const RouteSettings(name: "responsable"),
+      ),
+    );
+  }
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -162,15 +174,7 @@ class LoginScreen extends StatelessWidget {
                                     width: double.infinity,
                                     child: OutlinedButton.icon(
                                       onPressed: () =>
-                                          Navigator.of(context).push(
-                                            MaterialPageRoute(
-                                              builder: (_) =>
-                                                  const ResponsableScreen(),
-                                              settings: const RouteSettings(
-                                                name: "responsable",
-                                              ),
-                                            ),
-                                          ),
+                                          _identifierResponsable(context),
                                       icon: const Icon(
                                         Icons.person_outline,
                                         size: 16,