feat: Bandeau générique, dashboards et doc (squash develop, Closes #100)

- Bandeau générique (DashboardBandeau) pour Parent, Admin, Gestionnaire, AM
- ParentDashboardScreen, AdminDashboardScreen, GestionnaireDashboardScreen, AM dashboard
- AppFooter responsive, scripts Gitea (create/list issues parent API)
- Doc: ticket #101 Inscription Parent API, mise à jour 23_LISTE-TICKETS
- User.fromJson robustesse (nullable id/email/role)
- Suppression dashboard_app_bar.dart au profit de dashboard_bandeau.dart

Refs: #100, #101
Made-with: Cursor

frontend/lib/screens/gestionnaire/gestionnaire_dashboard_screen.dart

@@ -1,7 +1,9 @@
 import 'package:flutter/material.dart';
-import 'package:p_tits_pas/widgets/admin/dashboard_admin.dart';
+import 'package:p_tits_pas/models/user.dart';
+import 'package:p_tits_pas/services/auth_service.dart';
 import 'package:p_tits_pas/widgets/admin/user_management_panel.dart';
 import 'package:p_tits_pas/widgets/app_footer.dart';
+import 'package:p_tits_pas/widgets/dashboard/dashboard_bandeau.dart';
 
 /// Dashboard gestionnaire – même shell que l'admin, sans onglet Paramètres.
 /// Réutilise [UserManagementPanel].
@@ -14,24 +16,47 @@ class GestionnaireDashboardScreen extends StatefulWidget {
 }
 
 class _GestionnaireDashboardScreenState extends State<GestionnaireDashboardScreen> {
+  AppUser? _user;
+
+  @override
+  void initState() {
+    super.initState();
+    _loadUser();
+  }
+
+  Future<void> _loadUser() async {
+    final user = await AuthService.getCurrentUser();
+    if (mounted) setState(() => _user = user);
+  }
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: PreferredSize(
         preferredSize: const Size.fromHeight(60.0),
-        child: Container(
-          decoration: BoxDecoration(
-            border: Border(
-              bottom: BorderSide(color: Colors.grey.shade300),
-            ),
-          ),
-          child: DashboardAppBarAdmin(
-            selectedIndex: 0,
-            onTabChange: (_) {},
-            showSettingsTab: false,
-            roleLabel: 'Gestionnaire',
-            setupCompleted: true,
-          ),
+        child: DashboardBandeau(
+          tabItems: const [
+            DashboardTabItem(label: 'Gestion des utilisateurs'),
+          ],
+          selectedTabIndex: 0,
+          onTabSelected: (_) {},
+          userDisplayName: _user?.fullName.isNotEmpty == true
+              ? _user!.fullName
+              : 'Gestionnaire',
+          userEmail: _user?.email,
+          userRole: _user?.role,
+          onProfileTap: () {
+            ScaffoldMessenger.of(context).showSnackBar(
+              const SnackBar(content: Text('Modification du profil – à venir')),
+            );
+          },
+          onSettingsTap: () {
+            ScaffoldMessenger.of(context).showSnackBar(
+              const SnackBar(content: Text('Paramètres – à venir')),
+            );
+          },
+          onLogout: () {},
+          showLogoutConfirmation: true,
         ),
       ),
       body: Column(