SIENTIAPDE-1712

Remove code validation script and refactor imports in activities and workflows

- Deleted the `validate.sh` script, which was responsible for running code quality checks.
- Cleaned up import statements in `activities.py`, `gates.py`, `mlflow.py`, and `storage.py` by removing unused imports and organizing them.
- Refactored initialization methods in `MinioManager` and `MLFlow` classes for improved readability.
- Updated various workflows to ensure compatibility with the new structure and removed unnecessary comments.
- Enhanced test cases to accommodate changes in the activities and workflows, ensuring proper mocking of dependencies.

tests/conftest.py

@@ -1,3 +1,49 @@
+import os
+import sys
+from unittest.mock import MagicMock
+
+# The production code converts SIENTIA_MINIO_OFFLOAD_THRESHOLD_BYTES to int at import-time.
+# Tests must set it to a valid integer string to avoid import errors.
+os.environ.setdefault('SIENTIA_MINIO_OFFLOAD_THRESHOLD_BYTES', '1')
+
+
+class DummyMinioDataFramePayload:
+    """
+    Minimal payload double used by unit tests.
+
+    The production workflow/gates expect a MinioDataFramePayload-like object with:
+    - async retrieve(minio_repo, workflow_metadata) -> DataFrame | dict
+    - has_data() -> bool
+    - cleanup_prefix() -> str | None
+    - last_timestamp: attribute
+    - status: attribute
+    """
+
+    def __init__(
+        self,
+        *,
+        retrieve_return=None,
+        has_data: bool = True,
+        cleanup_prefix: str | None = None,
+        last_timestamp: str = '2024-01-01',
+        status: dict | None = None,
+    ):
+        self._retrieve_return = retrieve_return
+        self._has_data = has_data
+        self._cleanup_prefix = cleanup_prefix
+        self.last_timestamp = last_timestamp
+        self.status = status
+
+    async def retrieve(self, _minio_repo, _workflow_metadata=None):
+        return self._retrieve_return
+
+    def has_data(self) -> bool:
+        return self._has_data
+
+    def cleanup_prefix(self) -> str | None:
+        return self._cleanup_prefix
+
+
 """
 Pytest configuration file with global mocks for external dependencies.
 
@@ -6,9 +52,6 @@ during unit tests. The mock is registered in sys.modules before any test
 imports are executed.
 """
 
-import sys
-from unittest.mock import MagicMock
-
 # Mock sientia module
 sientia_mock = MagicMock()
 sientia_mock.ModelAnalysis = MagicMock