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/repositories/tenders_repository.dart

@@ -13,7 +13,8 @@ class TendersRepository {
 
   Future<Result<TendersResponse>> getTenders({
     required int limit,
-    required int offset,
+    int? offset,
+    String? cursor,
     String? query,
     String? sortBy,
     String? sortOrder,
@@ -23,6 +24,7 @@ class TendersRepository {
     return _tendersService.getTenders(
       limit: limit,
       offset: offset,
+      cursor: cursor,
       query: query,
       sortBy: sortBy,
       sortOrder: sortOrder,