Merge pull request #29227 from omrope79:object_detect_changes

Update BarcodeDetector super-resolution API to use single-file ONNX #29227

### Pull Request Readiness Checklist

This PR updates the `BarcodeDetector` super-resolution API to support and utilize a single-file ONNX model format. 

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/objdetect/src/barcode.cpp

@@ -339,22 +339,21 @@ bool BarcodeImpl::detectAndDecodeMulti(InputArray img, vector<string> &decoded_i
 // Public class implementation
 
 BarcodeDetector::BarcodeDetector()
-    : BarcodeDetector(string(), string())
+    : BarcodeDetector(std::string())
 {
 }
 
-BarcodeDetector::BarcodeDetector(const string &prototxt_path, const string &model_path)
+BarcodeDetector::BarcodeDetector(const string &super_resolution_model_path)
 {
     Ptr<BarcodeImpl> p_ = new BarcodeImpl();
     p = p_;
     p_->sr = make_shared<SuperScale>();
-    // The Super Resolution model is now a single-file ONNX network; the legacy Caffe
-    // prototxt argument is retained for API compatibility but is no longer used.
-    CV_UNUSED(prototxt_path);
-    if (!model_path.empty())
+    // The optional Super Resolution model is a single-file ONNX network (Caffe support
+    // has been removed). An empty path simply disables super resolution.
+    if (!super_resolution_model_path.empty())
     {
-        CV_Assert(utils::fs::exists(model_path));
-        int res = p_->sr->init(model_path);
+        CV_Assert(utils::fs::exists(super_resolution_model_path));
+        int res = p_->sr->init(super_resolution_model_path);
         CV_Assert(res == 0);
         p_->use_nn_sr = true;
     }