feat(dashboard-admin): connect admin dashboard to real API data (Ticket #92)

- Frontend:
  - Create UserService to handle user-related API calls (gestionnaires, parents, AMs, admins)
  - Update AdminDashboardScreen to use dynamic widgets
  - Implement dynamic management widgets:
    - GestionnaireManagementWidget
    - ParentManagementWidget
    - AssistanteMaternelleManagementWidget
    - AdminManagementWidget
  - Add data models: ParentModel, AssistanteMaternelleModel
  - Update AppUser model
  - Update ApiConfig

- Backend:
  - Update controllers (Parents, AMs, Gestionnaires, Users) to allow ADMINISTRATEUR role to list users
  - Note: Gestionnaires endpoint is currently bypassed in frontend (using /users filter) due to module import issue (documented in docs/92_NOTE-BACKEND-GESTIONNAIRES.md)

- Docs:
  - Add note about backend fix for Gestionnaires module
  - Update .cursorrules to forbid worktrees

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/lib/models/parent_model.dart

@@ -0,0 +1,18 @@
+import 'package:p_tits_pas/models/user.dart';
+
+class ParentModel {
+  final AppUser user;
+  final int childrenCount;
+
+  ParentModel({required this.user, this.childrenCount = 0});
+
+  factory ParentModel.fromJson(Map<String, dynamic> json) {
+    final userJson = json['user'] ?? json;
+    final user = AppUser.fromJson(userJson);
+    final children = json['parentChildren'] as List?;
+    return ParentModel(
+      user: user,
+      childrenCount: children?.length ?? 0,
+    );
+  }
+}