Merge pull request #27620 from killerdevildog:fix-scalar-typing-issue-27528

Fix Python Scalar typing issue #27528 #27620

- Add ScalarInput and ScalarOutput types for better type safety
- ScalarInput: Union[Sequence[float], float] for function parameters
- ScalarOutput: Sequence[float] for function return values
- Keep original Scalar type for backwards compatibility (deprecated)
- Add refinement functions to apply new types to specific functions
- Functions returning scalars now use ScalarOutput (mean, sumElems, trace)
- Drawing functions now use ScalarInput for color parameters
- Resolves MyPy compatibility issues with scalar return values
- Maintains full backwards compatibility

closes #27528 

### Pull Request Readiness Checklist

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
- [ ] 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/python/src2/typing_stubs_generation/api_refinement.py

@@ -28,6 +28,8 @@ def apply_manual_api_refinement(root: NamespaceNode) -> None:
     version_constant = root.add_constant("__version__", "<unused>")
     version_constant._value_type = "str"
 
+    convert_returned_scalar_to_tuple(root)
+
     """
     def redirectError(
         onError: Callable[[int, str, str, str, int], None] | None
@@ -126,6 +128,30 @@ def make_optional_arg(*arg_names: str) -> Callable[[NamespaceNode, SymbolName],
     return _make_optional_arg
 
 
+def convert_returned_scalar_to_tuple(root: NamespaceNode) -> None:
+    """Force `tuple[float, float, float, float]` usage instead of Scalar alias
+    for return types due to `pyopencv_from` specialization for Scalar type.
+    """
+
+    float_4_tuple_node = TupleTypeNode(
+        "ScalarOutput",
+        items=(PrimitiveTypeNode.float_(),) * 4
+    )
+
+    def fix_scalar_return_type(fn: FunctionNode.Overload):
+        if fn.return_type is None:
+            return
+        if fn.return_type.type_node.typename == "Scalar":
+            fn.return_type.type_node = float_4_tuple_node
+
+    for overload in for_each_function_overload(root):
+        fix_scalar_return_type(overload)
+
+    for ns in root.namespaces.values():
+        for overload in for_each_function_overload(ns):
+            fix_scalar_return_type(overload)
+
+
 def refine_cuda_module(root: NamespaceNode) -> None:
     def fix_cudaoptflow_enums_names() -> None:
         for class_name in ("NvidiaOpticalFlow_1_0", "NvidiaOpticalFlow_2_0"):