fix(file_storage): log orphaned thumbnail variant deletes (review round 1, pass 3)

Claude-Session: https://claude.ai/code/session_01M9neheZZEe3sVpDi2S3zT4

Author: antosubash

modules/file_storage/file_storage/thumbnails.py

@@ -17,6 +17,7 @@
 
 import asyncio
 import io
+import logging
 import struct
 import weakref
 from typing import TYPE_CHECKING
@@ -29,6 +30,8 @@
 if TYPE_CHECKING:
     from file_storage.contracts.service import StorageBackend
 
+_logger = logging.getLogger(__name__)
+
 
 class NotAnImageError(Exception):
     """The file's type has no thumbnail (not a raster image, or SVG)."""
@@ -206,7 +209,12 @@ async def _once():
 
 async def delete_variants(backend: StorageBackend, key: str) -> None:
     """Drop every cached variant of ``key``; absent ones are fine."""
-    await asyncio.gather(
+    results = await asyncio.gather(
         *(backend.delete(variant_key(key, width)) for width in constants.THUMBNAIL_WIDTHS),
         return_exceptions=True,
     )
+    for result in results:
+        # An absent variant is the common case; anything else is an orphan
+        # nobody would otherwise learn about.
+        if isinstance(result, Exception) and not isinstance(result, StorageNotFoundError):
+            _logger.warning("file_storage.variant_delete_failed key=%s error=%r", key, result)