🧹 Refactor ensure_group to take DatasetGroup object

[devdudumuniz]

🎯 What: The code health issue addressed
Refactored the ensure_group method in pysus/management/catalog.py which had too many parameters by consolidating the group-related arguments into a single DatasetGroup object (or string) parameter. Updated pysus/management/sync.py to leverage the new signature.

💡 Why: How this improves maintainability
This reduces the parameter count of ensure_group from 5 to 3 and makes the method's interface cleaner and more aligned with the domain models defined in pysus.api.metadata.models.

✅ Verification: How you confirmed the change is safe
Ran pylint against the modified files which showed a higher score and eliminated the "too many parameters" warning. Executed the complete pytest test suite which passed successfully with 1535 tests.

✨ Result: The improvement achieved
A cleaner API signature that maintains full backwards compatibility with edge cases via robust type checking logic (isinstance(group, DatasetGroup) versus str).

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PR created automatically by Jules for task 1135970874737693406 started by @devdudumuniz

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