Resolve linter contradictions: consolidate config, fix isort first-party, pylint 10/10

Agent-Logs-Url: https://github.com/christianlouis/dmarq/sessions/1e4a1f06-55b9-4040-853e-6aaf9ee574c8

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

backend/app/tests/test_reports_api.py

@@ -1,9 +1,10 @@
 import io
 import zipfile
 
-from app.tests.test_data import SAMPLE_XML
 from fastapi.testclient import TestClient
 
+from app.tests.test_data import SAMPLE_XML
+
 
 def _make_zip(xml_content: str) -> bytes:
     """Create a ZIP file containing the given XML content."""