Refactor tenders pagination and enhance API integration

- Updated TendersRepository and TendersService to support cursor-based pagination.
- Modified TendersViewModel to manage pagination state and handle API responses more effectively.
- Replaced existing pagination UI components with a new WindowedPagination widget across desktop, mobile, and tablet views.
- Improved notification handling in the UI to reflect the presence of notifications dynamically.
- Adjusted main tenders slider to ensure proper rendering based on the current page index.

lib/data/services/api/tenders_api.dart

@@ -4,14 +4,20 @@ class TendersApi {
   static const String tenders = '/api/v1/tenders';
   static String getTenders({
     required int limit,
-    required int offset,
+    int? offset,
+    String? cursor,
     String? query,
     String? sortBy,
     String? sortOrder,
     String? publicationDateFrom,
     String? publicationDateTo,
   }) {
-    String url = '$tenders?limit=$limit&offset=$offset';
+    String url = '$tenders?limit=$limit';
+    if (cursor != null && cursor.isNotEmpty) {
+      url += '&cursor=${Uri.encodeComponent(cursor)}';
+    } else if (offset != null) {
+      url += '&offset=$offset';
+    }
     if (query != null && query.isNotEmpty) {
       url += '&q=${Uri.encodeComponent(query)}';
     }