fix(db): collapse presentation-key groups without min(uuid)

PostgreSQL has no min(uuid) aggregate, so every query that picked a group
representative with MIN over the item id failed with 42883: library browse,
search, Recently Added, the by-name endpoints and Upcoming.

- Pick the representative with an anti-join on (primary version, id)
- Cover the collapse with a repository test against a real PostgreSQL

Jellyfin.Server.Implementations/Item/BaseItemRepository.ByName.cs

@@ -219,9 +219,11 @@ public sealed partial class BaseItemRepository
         }
         else
         {
+            // The representative is the row no other row in its group sorts before, not MIN(Id):
+            // PostgreSQL has no min(uuid) aggregate, while comparing two uuids is supported everywhere.
             representativeIds = masterQuery
-                .GroupBy(e => e.PresentationUniqueKey)
-                .Select(g => g.Min(e => e.Id))
+                .Where(e => !masterQuery.Any(o => o.PresentationUniqueKey == e.PresentationUniqueKey && o.Id.CompareTo(e.Id) < 0))
+                .Select(e => e.Id)
                 .ToList();
         }