chore: fix all ruff lint warnings (unused imports, unsorted imports, unused vars)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_ice_extraction.py

@@ -1,10 +1,8 @@
 """Tests for ICE extraction: format detection, XLS parsing, API client."""
 
 import csv
-import gzip
 import io
-import struct
-from unittest.mock import MagicMock, patch
+from unittest.mock import MagicMock
 
 import pytest
 import xlwt  # noqa: F401 — needed to create XLS fixtures; skip tests if missing
@@ -96,7 +94,7 @@ def test_fetch_report_listings_parses_response():
         _make_api_row("Certified Stock Aging Report", "/dl/aging.xls"),
     ])
 
-    from ice_stocks.ice_api import ICE_BASE_URL, fetch_report_listings
+    from ice_stocks.ice_api import ICE_BASE_URL
     rows = fetch_report_listings(mock_session, product_id=2)
 
     assert len(rows) == 2
@@ -113,7 +111,6 @@ def test_fetch_report_listings_prepends_base_url_for_absolute():
         _make_api_row("Test", "https://other.example.com/file.xls"),
     ])
 
-    from ice_stocks.ice_api import fetch_report_listings
     rows = fetch_report_listings(mock_session, product_id=2)
     assert rows[0]["download_url"] == "https://other.example.com/file.xls"