chore(downloads): log failed resolutions and tighten retry dataclass/tests

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

backend/app/tasks/downloads.py

@@ -119,7 +119,7 @@ def _extract_vanity_from_url(url: str) -> Optional[str]:
 class _DownloadAttempt:
     """Result of executing a download, possibly with a retry after campaign-ID resolution."""
     dl_result: DownloadResult
-    resolved_campaign_id: Optional[str]
+    resolved_campaign_id: Optional[str] = None
 
 
 async def _execute_download_with_retry(
@@ -176,6 +176,11 @@ async def _execute_download_with_retry(
                 return _DownloadAttempt(
                     dl_result=retry_result, resolved_campaign_id=campaign_id
                 )
+            else:
+                logger.warning(
+                    f"Could not resolve campaign ID for {subscription_name}/patreon ({vanity}); "
+                    f"original failure will be recorded"
+                )
 
     return _DownloadAttempt(dl_result=dl_result, resolved_campaign_id=None)
 

backend/tests/tasks/test_downloads_patreon_retry.py

@@ -197,6 +197,7 @@ async def test_unextractable_vanity_skips_retry(monkeypatch):
     )
 
     assert result.dl_result is failure
+    assert result.resolved_campaign_id is None
     resolver_mock.assert_not_called()
     assert gdl.download.call_count == 1