Refactor: rename BottomNavigation and update TendersScreen structure

- Renamed BottomNavigation to TenderBottomNavigation for clarity.
- Updated TendersScreen to use TenderBottomNavigation.
- Converted TendersScreen from StatelessWidget to StatefulWidget to manage tab state.
- Added TabController for handling tab changes and improved layout with SafeArea and PageView.

lib/views/tenders/widgets/tab_item.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+
+import '../../../core/constants/colors.dart';
+import '../../../core/utils/size_config.dart';
+
+class TabItem extends StatelessWidget {
+  const TabItem({
+    super.key,
+    required this.title,
+    required this.isActive,
+    required this.onTap,
+  });
+
+  final String title;
+  final bool isActive;
+  final VoidCallback onTap;
+
+  @override
+  Widget build(BuildContext context) {
+    return InkWell(
+      onTap: onTap,
+      child: Tab(
+        child: SizedBox(
+          width: 170.0.w(),
+          child: Center(
+            child: Text(
+              title,
+              style: TextStyle(
+                fontSize: 16.0.sp(),
+                fontWeight: FontWeight.w600,
+                color: isActive ? AppColors.mainBlue : AppColors.grey60,
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}