fix(fc3c): ruff — split SyncSession import, StrEnum, ASYNC240 noqa, blank-line

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/services/download_service.py

@@ -20,7 +20,8 @@ from typing import Any
 
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
-from sqlalchemy.orm import Session as SyncSession, joinedload
+from sqlalchemy.orm import Session as SyncSession
+from sqlalchemy.orm import joinedload
 
 from ..models import Artist, DownloadEvent, Source
 from .credential_service import CredentialService
@@ -217,7 +218,10 @@ class DownloadService:
             if path_str in (dl_result.quarantined_paths or []):
                 continue
             path = Path(path_str)
-            if not path.exists():
+            # Sync stdlib filesystem ops are intentional here: this orchestrator
+            # runs under `asyncio.run` inside a Celery task — no other awaitables
+            # compete for the loop. ASYNC240 suppressed below.
+            if not path.exists():  # noqa: ASYNC240
                 continue
 
             def _attach(p=path):
@@ -230,7 +234,7 @@ class DownloadService:
             if result.status in ("imported", "superseded"):
                 import_summary["attached"] += 1
                 try:
-                    bytes_downloaded += path.stat().st_size
+                    bytes_downloaded += path.stat().st_size  # noqa: ASYNC240
                 except OSError:
                     pass
             elif result.status == "skipped" and result.skip_reason and result.skip_reason.value in (
@@ -238,7 +242,7 @@ class DownloadService:
             ):
                 import_summary["skipped"] += 1
                 try:
-                    path.unlink(missing_ok=True)
+                    path.unlink(missing_ok=True)  # noqa: ASYNC240
                 except OSError:
                     pass
             else: