test: fix CSV reporter test fixtures to match Assessment validation

Updated mock_assessment fixture to use attributes_total=0 with
findings=[] to match the Assessment model validation that requires
findings count to equal attributes_total.

This is consistent with the fix already applied to
test_multi_html_reporter.py.

Author: jeremyeder

tests/unit/test_csv_reporter.py

@@ -57,9 +57,9 @@ def mock_assessment(mock_repository):
         timestamp=datetime(2025, 1, 22, 14, 30, 22),
         overall_score=85.5,
         certification_level="Gold",
-        attributes_assessed=20,
-        attributes_not_assessed=5,
-        attributes_total=25,
+        attributes_assessed=0,
+        attributes_not_assessed=0,
+        attributes_total=0,
         findings=[],
         config=None,
         duration_seconds=42.5,