Add Pagination Model for API Responses

Added a new Pagination class to model the pagination data that comes with API responses. This will help in handling paginated data more effectively and transparently.

The Pagination class includes fields for total items, total pages, current page, and page size. It also includes a factory constructor for creating an instance from a JSON object.

lib/models/pagination.dart

@@ -0,0 +1,22 @@
+class Pagination {
+  final int totalItems;
+  final int totalPages;
+  final int currentPage;
+  final int pageSize;
+
+  Pagination({
+    required this.totalItems,
+    required this.totalPages,
+    required this.currentPage,
+    required this.pageSize,
+  });
+
+  factory Pagination.fromJson(Map<String, dynamic> json) {
+    return Pagination(
+      totalItems: json['total_items'],
+      totalPages: json['total_pages'],
+      currentPage: json['current_page'],
+      pageSize: json['page_size'],
+    );
+  }
+}