feat(#159/#160): suppressions métier dashboard — API + UI (squash develop).

Matrice PO #154 : supprimer dossiers famille/AM, parents, enfants et comptes
staff avec règles métier (placements clôturés, sans_enfant, cascade foyer,
droits gestionnaire/admin). Poubelle en liste, dialogues de confirmation,
garde-fou gestionnaire→gestionnaire. Inclut polish hauteur modale fiche AM.

frontend/lib/widgets/admin/admin_management_widget.dart

@@ -4,7 +4,9 @@ import 'package:p_tits_pas/utils/phone_utils.dart';
 import 'package:p_tits_pas/screens/administrateurs/creation/gestionnaires_create.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_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';
 
 class AdminManagementWidget extends StatefulWidget {
@@ -24,6 +26,7 @@ class _AdminManagementWidgetState extends State<AdminManagementWidget> {
   String? _error;
   List<AppUser> _admins = [];
   String? _currentUserRole;
+  String? _currentUserId;
 
   @override
   void initState() {
@@ -62,6 +65,7 @@ class _AdminManagementWidgetState extends State<AdminManagementWidget> {
     if (cached != null) {
       setState(() {
         _currentUserRole = (cached.role).toLowerCase();
+        _currentUserId = cached.id;
       });
       return;
     }
@@ -69,6 +73,7 @@ class _AdminManagementWidgetState extends State<AdminManagementWidget> {
     if (!mounted || refreshed == null) return;
     setState(() {
       _currentUserRole = (refreshed.role).toLowerCase();
+      _currentUserId = refreshed.id;
     });
   }
 
@@ -79,6 +84,16 @@ class _AdminManagementWidgetState extends State<AdminManagementWidget> {
     return _currentUserRole == 'super_admin';
   }
 
+  bool _canDeleteAdmin(AppUser target) {
+    return canDeleteAdministrateur(
+      currentRole: _currentUserRole,
+      currentUserId: _currentUserId,
+      targetUserId: target.id,
+      targetRole: target.role,
+      adminCount: _admins.length,
+    );
+  }
+
   Future<void> _openAdminEditDialog(AppUser user) async {
     final canEdit = _canEditAdmin(user);
     final changed = await showDialog<bool>(
@@ -98,6 +113,56 @@ class _AdminManagementWidgetState extends State<AdminManagementWidget> {
     }
   }
 
+  Future<void> _confirmDelete(AppUser user) async {
+    final blocked = adminDeleteBlockedReason(
+      currentRole: _currentUserRole,
+      currentUserId: _currentUserId,
+      targetUserId: user.id,
+      targetRole: user.role,
+      adminCount: _admins.length,
+    );
+    if (blocked != null) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text(blocked)),
+      );
+      return;
+    }
+
+    final name = user.fullName.isNotEmpty ? user.fullName : user.email;
+    final isLast = _admins.length <= 1;
+    final confirmed = await showSuppressionConfirmDialog(
+      context,
+      title: 'Supprimer l\'administrateur',
+      people: [SuppressionPersonLine.administrateur(name)],
+      footnotes: [
+        if (isLast)
+          'Attention : c’est le dernier administrateur.',
+        'Le compte sera définitivement supprimé.',
+      ],
+    );
+    if (!confirmed || !mounted) return;
+
+    try {
+      final result = await UserService.deleteUser(user.id);
+      if (!mounted) return;
+      final msg =
+          (result['message'] ?? 'Administrateur supprimé.').toString();
+      ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text(msg)));
+      await _loadAdmins();
+    } catch (e) {
+      if (!mounted) return;
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(
+          content: Text(
+            e is Exception
+                ? e.toString().replaceFirst('Exception: ', '')
+                : 'Erreur suppression',
+          ),
+        ),
+      );
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
     final query = widget.searchQuery.toLowerCase();
@@ -117,6 +182,7 @@ class _AdminManagementWidgetState extends State<AdminManagementWidget> {
         final user = filteredAdmins[index];
         final isSuperAdmin = _isSuperAdmin(user);
         final canEdit = _canEditAdmin(user);
+        final canDelete = _canDeleteAdmin(user);
         return AdminUserCard(
           title: user.fullName,
           fallbackIcon: isSuperAdmin
@@ -148,6 +214,8 @@ class _AdminManagementWidgetState extends State<AdminManagementWidget> {
                 _openAdminEditDialog(user);
               },
             ),
+            if (canDelete)
+              suppressionIconButton(onPressed: () => _confirmDelete(user)),
           ],
         );
       },