feat: mark prior failures as superseded on successful download

backend/app/tasks/downloads.py

@@ -5,7 +5,7 @@ import logging
 from datetime import datetime, timedelta
 from typing import Optional
 
-from sqlalchemy import select, and_, or_
+from sqlalchemy import select, and_, or_, update
 from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
 from sqlalchemy.orm import selectinload
 
@@ -300,6 +300,16 @@ async def _download_source_async(source_id: int, download_id: int = None) -> dic
                 source.error_count = 0
                 logger.info(f"Download completed for {subscription_name}/{source_platform}: {dl_result.files_downloaded} files")
 
+                # Mark any prior failures for this source as superseded
+                await session.execute(
+                    update(Download)
+                    .where(
+                        Download.source_id == source_id,
+                        Download.status == DownloadStatus.FAILED,
+                    )
+                    .values(superseded=True)
+                )
+
                 publish_event("download.completed", {
                     "download_id": actual_download_id,
                     "source_id": source_id,