Update iOS deployment target to 13.0, enhance Flutter integration, and improve tender submission flow

- Changed the iOS deployment target from 12.0 to 13.0 in Podfile and project settings.
- Updated AppDelegate to support implicit Flutter engine initialization.
- Modified Info.plist to include scene configuration for multiple scenes.
- Enhanced CompletionOfDocumentsRouteData to accept a tenderId parameter.
- Implemented tender submission functionality in TenderDetailViewModel and updated UI components to reflect loading states and success/error messages.
- Added new strings for submission success and error notifications.

lib/view_models/tender_detail_view_model.dart

@@ -6,6 +6,7 @@ import 'package:tm_app/data/services/model/tender_data/tender_data.dart';
 import 'package:tm_app/data/services/model/tender_detail_response/tender_detail_response_model.dart';
 
 import '../core/constants/tender_approval_status.dart';
+import '../core/constants/tender_submision_mode.dart';
 import '../data/services/model/tender_approvals_by_id_response/tender_approvals_by_id_response.dart';
 import '../data/services/model/tender_approvals_data/tender_approvals_data.dart';
 import '../data/services/model/tender_approvals_toggle_response/tender_approvals_toggle_response.dart';
@@ -143,4 +144,33 @@ class TenderDetailViewModel with ChangeNotifier {
     _errorMessage = null;
     notifyListeners();
   }
+
+  /// Submits the tender for completion via the self-apply flow.
+  /// POSTs to /api/v1/tender-approvals with status "submitted" and
+  /// submission_mode "self-apply". Returns true on success.
+  Future<bool> submitForCompletion({required String tenderId}) async {
+    _isSubmitApprovalLoading = true;
+    _errorMessage = null;
+    notifyListeners();
+
+    bool success = false;
+    final result = await _tendersRepository.toggleApprovals(
+      tenderId: tenderId,
+      status: TenderApprovalStatus.submitted.value,
+      submissionMode: TenderSubmissionMode.selfApply.value,
+    );
+    switch (result) {
+      case Ok<TenderApprovalsToggleResponse>():
+        success = true;
+        _status = result.value.data?.status ?? '';
+        break;
+      case Error<TenderApprovalsToggleResponse>():
+        _errorMessage = result.error.toString();
+        break;
+    }
+
+    _isSubmitApprovalLoading = false;
+    notifyListeners();
+    return success;
+  }
 }