fix timezone handling and logging fallback robustness

src/vlm/scanner.py

@@ -20,6 +20,13 @@ from vlm.models import VideoFile
 logger = logging.getLogger(__name__)
 
 
+def _normalize_to_utc(timestamp: datetime) -> datetime:
+    """Normalize a datetime to a UTC instant."""
+    if timestamp.tzinfo is None:
+        timestamp = timestamp.astimezone()
+    return timestamp.astimezone(timezone.utc)
+
+
 def scan_library(root: Path, config: Config) -> list[VideoFile]:
     """Recursively scan library for video files.
     
@@ -50,8 +57,6 @@ def scan_library(root: Path, config: Config) -> list[VideoFile]:
     
     video_files = []
     file_count = 0
-    error_count = 0
-    
     # Recursively scan directory tree
     for video_file in _scan_directory_recursive(root, config, root):
         video_files.append(video_file)
@@ -61,9 +66,6 @@ def scan_library(root: Path, config: Config) -> list[VideoFile]:
             logger.debug(f"Scanned {file_count} files so far...")
     
     logger.info(f"Scan complete. Found {file_count} video files")
-    if error_count > 0:
-        logger.warning(f"Encountered {error_count} errors during scan (see log for details)")
-    
     return video_files
 
 
@@ -145,7 +147,7 @@ def _create_video_file(file_path: Path, library_root: Path) -> Optional[VideoFil
         # Get file stats
         stat = file_path.stat()
         size_bytes = stat.st_size
-        modified_timestamp = datetime.fromtimestamp(stat.st_mtime)
+        modified_timestamp = datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc)
         
         # Categorize based on directory structure
         category = categorize_file(file_path, library_root)
@@ -376,11 +378,7 @@ def save_inventory_csv(files: list[VideoFile], output: Path, library_root: Path)
         # Write each file
         for video_file in files:
             # Format timestamp as ISO 8601 in UTC
-            if video_file.modified_timestamp.tzinfo is None:
-                # Assume local time, convert to UTC
-                modified_utc = video_file.modified_timestamp.replace(tzinfo=timezone.utc)
-            else:
-                modified_utc = video_file.modified_timestamp.astimezone(timezone.utc)
+            modified_utc = _normalize_to_utc(video_file.modified_timestamp)
             
             row = {
                 'path': str(video_file.path),
@@ -434,11 +432,7 @@ def save_inventory_json(files: list[VideoFile], output: Path, library_root: Path
     # Add each file
     for video_file in files:
         # Format timestamp as ISO 8601 in UTC
-        if video_file.modified_timestamp.tzinfo is None:
-            # Assume local time, convert to UTC
-            modified_utc = video_file.modified_timestamp.replace(tzinfo=timezone.utc)
-        else:
-            modified_utc = video_file.modified_timestamp.astimezone(timezone.utc)
+        modified_utc = _normalize_to_utc(video_file.modified_timestamp)
         
         file_data = {
             'path': str(video_file.path),