fix: delete stale package_downloads rows when removing deleted packages (#440)

* fix: delete stale package_downloads rows when removing deleted packages

When the worker detects a deleted/unlisted package (NuGet API returns
null), it removes the catalog entry but leaves the package_downloads
record behind. The orphaned row keeps being re-queued by the publisher
every day since its LatestDownloadCountCheckedUtc is never updated.

In integration tests this causes WaitForAllPackagesProcessed to time
out because GetUnprocessedPackageIds never reaches zero.

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

* address review: wrap both deletes in a transaction

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

* fix: finish Sentry span only after transaction commit

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: bruno-garcia

src/NuGetTrends.Scheduler/DailyDownloadWorker.cs

@@ -423,16 +423,30 @@ await _clickHouseService.InsertDailyDownloadsAsync(
         // Handle deleted packages (batch query to avoid N+1)
         if (deletedPackageIds.Count > 0)
         {
-            var deleteSpan = StartDbSpan(parentSpan, "DELETE FROM package_details_catalog_leafs WHERE package_id_lowered IN (...)", "postgresql", "DELETE");
+            var loweredIds = deletedPackageIds.Select(id => id.ToLowerInvariant()).Distinct().ToList();
+
+            var deleteSpan = StartDbSpan(parentSpan,
+                "DELETE FROM package_details_catalog_leafs, package_downloads WHERE package_id_lowered IN (...)",
+                "postgresql", "DELETE");
             deleteSpan.SetTag("count", deletedPackageIds.Count.ToString());
             try
             {
-                var loweredIds = deletedPackageIds.Select(id => id.ToLowerInvariant()).Distinct().ToList();
-                var deletedCount = await context.PackageDetailsCatalogLeafs
+                await using var transaction = await context.Database.BeginTransactionAsync(_cancellationTokenSource.Token);
+
+                var deletedCatalogCount = await context.PackageDetailsCatalogLeafs
+                    .Where(p => loweredIds.Contains(p.PackageIdLowered))
+                    .ExecuteDeleteAsync(_cancellationTokenSource.Token);
+
+                // Also remove stale package_downloads records so the publisher
+                // doesn't keep re-queuing packages that no longer exist.
+                var deletedDownloadsCount = await context.PackageDownloads
                     .Where(p => loweredIds.Contains(p.PackageIdLowered))
                     .ExecuteDeleteAsync(_cancellationTokenSource.Token);
 
-                deleteSpan.SetData("db.rows_affected", deletedCount);
+                await transaction.CommitAsync(_cancellationTokenSource.Token);
+
+                deleteSpan.SetData("db.catalog_rows_affected", deletedCatalogCount);
+                deleteSpan.SetData("db.downloads_rows_affected", deletedDownloadsCount);
                 deleteSpan.Finish(SpanStatus.Ok);
             }
             catch (Exception e)