Replace pydicom-seg with highdicom and upgrade pydicom to 3.0.1

Major changes:
- Replace unmaintained pydicom-seg library with well-established highdicom
- Upgrade pydicom from 2.4.4 to 3.0.1, enabling HTJ2K support

Refactoring in monailabel/datastore/utils/convert.py:
- Split nifti_to_dicom_seg into dispatcher + two implementations:
  * _highdicom_nifti_to_dicom_seg: Highdicom-based conversion
  * _itk_nifti_to_dicom_seg: Dcmqi/itkimage2segimage conversion
- Rename itk_image_to_dicom_seg → _dcmqi_nifti_to_dicom_seg for consistency

Tests in tests/unit/datastore/test_convert.py:
- Test both highdicom and ITK implementations via helper methods
- Validate metadata preservation, geometry, pixel data, and segment remapping
- Tests for non-sequential label remapping (1,5,10 → 1,2,3)
- Round-trip conversion tests with 3% tolerance for both implementations
- Handle ITK-specific behavior (stores only non-empty slices)

Minor improvements:
- Update pynrrd from 1.0.0 to 1.1.3 (former caused problem with numpy 2.x)
- Add documentation for optional dcmqi dependency

Signed-off-by: Joaquin Anton Guirao <[email protected]>

[pre-commit.ci] auto fixes from pre-commit.com hooks

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Code review fixes

Signed-off-by: Joaquin Anton Guirao <[email protected]>

[pre-commit.ci] auto fixes from pre-commit.com hooks

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Signed-off-by: Joaquin Anton Guirao <[email protected]>

More code review fixes

Signed-off-by: Joaquin Anton Guirao <[email protected]>

More fixes

Signed-off-by: Joaquin Anton Guirao <[email protected]>

[pre-commit.ci] auto fixes from pre-commit.com hooks

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Author: jantonguirao

monailabel/config.py

@@ -18,7 +18,7 @@
 
 
 def is_package_installed(name):
-    return name in (x.metadata.get("Name") for x in distributions())
+    return name in (x.metadata.get("Name") for x in distributions() if x.metadata is not None)
 
 
 class Settings(BaseSettings):