refactor(#155): option C — widgets partagés sans préfixe Admin.

Déplace les composants Admin* du dashboard partagé vers
widgets/dashboard/ (ChildDetailModal, AmEditModal, UserCard, Select*, …).
Conserve AdminManagementWidget et screens/administrateurs. Rename mécanique,
aucun changement de comportement.

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

frontend/lib/widgets/admin/parent_managmant_widget.dart

@@ -4,8 +4,8 @@ import 'package:p_tits_pas/models/parent_model.dart';
 import 'package:p_tits_pas/services/auth_service.dart';
 import 'package:p_tits_pas/services/user_service.dart';
 import 'package:p_tits_pas/utils/staff_deletion_rights.dart';
-import 'package:p_tits_pas/widgets/admin/common/admin_parent_edit_modal.dart';
-import 'package:p_tits_pas/widgets/admin/common/admin_user_card.dart';
+import 'package:p_tits_pas/widgets/dashboard/parent_edit_modal.dart';
+import 'package:p_tits_pas/widgets/dashboard/user_card.dart';
 import 'package:p_tits_pas/widgets/admin/common/suppression_confirm_dialog.dart';
 import 'package:p_tits_pas/widgets/admin/common/user_list.dart';
 
@@ -146,7 +146,7 @@ class _ParentManagementWidgetState extends State<ParentManagementWidget> {
       itemCount: filteredParents.length,
       itemBuilder: (context, index) {
         final parent = filteredParents[index];
-        return AdminUserCard(
+        return UserCard(
           title: parent.user.fullName,
           fallbackIcon: Icons.supervisor_account_outlined,
           avatarUrl: parent.user.photoUrl,
@@ -189,7 +189,7 @@ class _ParentManagementWidgetState extends State<ParentManagementWidget> {
   void _openParentDetails(ParentModel parent) {
     showDialog<void>(
       context: context,
-      builder: (context) => AdminParentEditModal(
+      builder: (context) => ParentEditModal(
         parent: parent,
         onSaved: _loadParents,
       ),