fix timezone handling and logging fallback robustness

tests/test_scanner.py

@@ -2,7 +2,8 @@
 
 import os
 import tempfile
-from datetime import datetime
+import time
+from datetime import datetime, timezone
 from pathlib import Path
 from unittest.mock import patch, MagicMock
 import subprocess
@@ -125,6 +126,7 @@ class TestScanLibrary:
         assert vf.path == video_file
         assert vf.size_bytes > 0
         assert isinstance(vf.modified_timestamp, datetime)
+        assert vf.modified_timestamp.tzinfo == timezone.utc
         assert vf.category == "movie"
     
     def test_scan_categorizes_files(self, tmp_path):
@@ -867,3 +869,37 @@ class TestInventoryReports:
         assert csv_row['category'] == json_file_data['category']
         assert csv_row['resolution'] == json_file_data['resolution']
         assert csv_row['codec'] == json_file_data['codec']
+
+    @pytest.mark.skipif(not hasattr(time, "tzset"), reason="tzset not available on this platform")
+    def test_save_inventory_csv_converts_naive_local_time_to_utc(self, tmp_path, monkeypatch):
+        """Test naive timestamps are interpreted as local time and converted to UTC."""
+        original_tz = os.environ.get("TZ")
+        try:
+            monkeypatch.setenv("TZ", "Etc/GMT-2")
+            time.tzset()
+
+            naive_local = datetime(2024, 1, 15, 10, 30, 0)
+            expected_utc = naive_local.astimezone(timezone.utc).strftime("%Y-%m-%dT%H:%M:%S")
+
+            video_files = [
+                VideoFile(
+                    path=Path("/library/movie/test.mp4"),
+                    filename="test.mp4",
+                    size_bytes=1024000,
+                    modified_timestamp=naive_local,
+                    category="movie"
+                )
+            ]
+
+            output_file = tmp_path / "inventory.csv"
+            from vlm.scanner import save_inventory_csv
+            save_inventory_csv(video_files, output_file, Path("/library"))
+
+            content = output_file.read_text(encoding="utf-8")
+            assert expected_utc in content
+        finally:
+            if original_tz is None:
+                monkeypatch.delenv("TZ", raising=False)
+            else:
+                monkeypatch.setenv("TZ", original_tz)
+            time.tzset()