feat: replace _not_superseded_condition subquery with superseded column filter

backend/app/api/downloads.py

@@ -23,6 +23,7 @@ async def list_downloads():
     status = request.args.get("status")
     from_date = request.args.get("from_date")
     to_date = request.args.get("to_date")
+    exclude_superseded = request.args.get("exclude_superseded", "").lower() in ("true", "1", "yes")
     page = int(request.args.get("page", 1))
     per_page = min(int(request.args.get("per_page", 50)), 100)
 
@@ -44,6 +45,9 @@ async def list_downloads():
             filters.append(Download.created_at >= datetime.fromisoformat(from_date))
         if to_date:
             filters.append(Download.created_at <= datetime.fromisoformat(to_date))
+        # When filtering failed downloads, optionally exclude ones superseded by a later success
+        if exclude_superseded and status == DownloadStatus.FAILED:
+            filters.append(Download.superseded == False)
 
         if filters:
             query = query.where(and_(*filters))
@@ -161,15 +165,18 @@ async def recent_activity():
         session = AsyncSession(bind=conn)
 
         # Get failed downloads OR completed with files (noteworthy activity)
-        # Eager load source and subscription for labeling
-        from sqlalchemy import or_
+        # Exclude failed downloads that have been superseded by a later success
+        # for the same source - those are stale failures the user doesn't need to see
         query = select(Download).options(
             selectinload(Download.source).selectinload(Source.subscription)
         ).where(
             and_(
                 Download.created_at >= cutoff,
                 or_(
-                    Download.status == DownloadStatus.FAILED,
+                    and_(
+                        Download.status == DownloadStatus.FAILED,
+                        Download.superseded == False,
+                    ),
                     and_(
                         Download.status == DownloadStatus.COMPLETED,
                         Download.file_count > 0
@@ -306,12 +313,23 @@ async def get_stats():
         recent_result = await session.execute(recent_query)
         recent_completed = recent_result.scalar()
 
+        # Active failed: failures not superseded by a later success for the same source
+        active_failed_query = select(func.count()).select_from(Download).where(
+            and_(
+                Download.status == DownloadStatus.FAILED,
+                Download.superseded == False,
+            )
+        )
+        active_failed_result = await session.execute(active_failed_query)
+        active_failed = active_failed_result.scalar()
+
         return jsonify({
             "total": sum(status_counts.values()),
             "by_status": status_counts,
             "by_platform": platform_counts,
             "completed": status_counts.get(DownloadStatus.COMPLETED, 0),
             "failed": status_counts.get(DownloadStatus.FAILED, 0),
+            "active_failed": active_failed,
             "pending": status_counts.get(DownloadStatus.PENDING, 0),
             "queued": status_counts.get(DownloadStatus.QUEUED, 0),
             "running": status_counts.get(DownloadStatus.RUNNING, 0),