feat: Enhance group and trip management with group creation and account linking

NOT FUNCTIONNAL

lib/blocs/group/group_state.dart

@@ -30,6 +30,18 @@ class GroupLoaded extends GroupState {
   const GroupLoaded(this.groups);
 }
 
+class GroupCreated extends GroupState {
+  final String groupId;
+  final String message;
+
+  const GroupCreated({
+    required this.groupId,
+    this.message = 'Groupe créé avec succès',
+  });
+  @override
+  List<Object?> get props => [groupId, message];
+}
+
 // Succès d'une opération
 class GroupOperationSuccess extends GroupState {
   final String message;