feat(#140): fiches admin famille — IdentityBlock, parsing enfants et avatars web

Extrait IdentityBlock réutilisable, aligne les modales parent/enfant sur le style validation, corrige le parsing parentChildren et les URLs /uploads en Flutter web.

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

frontend/lib/models/parent_child_summary.dart

@@ -23,9 +23,38 @@ class ParentChildSummary {
   factory ParentChildSummary.fromJson(Map<String, dynamic> json) {
     return ParentChildSummary(
       id: (json['id'] ?? '').toString(),
-      firstName: json['first_name'] as String?,
-      lastName: json['last_name'] as String?,
-      status: (json['status'] ?? '').toString(),
+      firstName: (json['first_name'] ?? json['prenom'])?.toString(),
+      lastName: (json['last_name'] ?? json['nom'])?.toString(),
+      status: (json['status'] ?? json['statut'] ?? '').toString(),
     );
   }
+
+  /// Parse un lien `parentChildren` (objet enfant imbriqué ou id seul).
+  static ParentChildSummary? fromParentChildLink(Map<String, dynamic> link) {
+    final childRaw = link['child'] ?? link['enfant'];
+    if (childRaw is Map) {
+      return ParentChildSummary.fromJson(Map<String, dynamic>.from(childRaw));
+    }
+
+    if (link.containsKey('first_name') ||
+        link.containsKey('prenom') ||
+        link.containsKey('id')) {
+      final id = (link['id'] ?? '').toString();
+      if (id.isNotEmpty &&
+          (link.containsKey('first_name') || link.containsKey('prenom'))) {
+        return ParentChildSummary.fromJson(link);
+      }
+    }
+
+    final enfantId =
+        link['enfantId'] ?? link['id_enfant'] ?? link['enfant_id'];
+    if (enfantId != null && enfantId.toString().isNotEmpty) {
+      return ParentChildSummary(
+        id: enfantId.toString(),
+        status: '',
+      );
+    }
+
+    return null;
+  }
 }