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.QueryBuilding.cs

@@ -96,22 +96,36 @@ public sealed partial class BaseItemRepository
         // primary version (PrimaryVersionId is null) so detail pages and actions target it instead
         // of an arbitrary alternate. Keep the grouped ids as an IQueryable sub-select; materializing
         // to a List would inline one bound parameter per id and hit SQLite's variable cap.
+        // 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.
+        // The anti-join reads the filtered set twice, so it has to close over a local that the
+        // reassignment below cannot reach - capturing dbQuery itself makes the tree self-referential.
+        var candidates = dbQuery;
         var enableGroupByPresentationUniqueKey = EnableGroupByPresentationUniqueKey(filter);
         if (enableGroupByPresentationUniqueKey && filter.GroupBySeriesPresentationUniqueKey)
         {
-            var groupedIds = dbQuery.GroupBy(e => new { e.PresentationUniqueKey, e.SeriesPresentationUniqueKey })
-                .Select(g => g.Where(e => e.PrimaryVersionId == null).Min(e => (Guid?)e.Id) ?? g.Min(e => (Guid?)e.Id));
+            var groupedIds = candidates
+                .Where(e => !candidates.Any(o => o.PresentationUniqueKey == e.PresentationUniqueKey
+                    && o.SeriesPresentationUniqueKey == e.SeriesPresentationUniqueKey
+                    && ((o.PrimaryVersionId == null && e.PrimaryVersionId != null)
+                        || ((o.PrimaryVersionId == null) == (e.PrimaryVersionId == null) && o.Id.CompareTo(e.Id) < 0))))
+                .Select(e => e.Id);
             dbQuery = context.BaseItems.AsNoTracking().Where(e => groupedIds.Contains(e.Id));
         }
         else if (enableGroupByPresentationUniqueKey)
         {
-            var groupedIds = dbQuery.GroupBy(e => e.PresentationUniqueKey)
-                .Select(g => g.Where(e => e.PrimaryVersionId == null).Min(e => (Guid?)e.Id) ?? g.Min(e => (Guid?)e.Id));
+            var groupedIds = candidates
+                .Where(e => !candidates.Any(o => o.PresentationUniqueKey == e.PresentationUniqueKey
+                    && ((o.PrimaryVersionId == null && e.PrimaryVersionId != null)
+                        || ((o.PrimaryVersionId == null) == (e.PrimaryVersionId == null) && o.Id.CompareTo(e.Id) < 0))))
+                .Select(e => e.Id);
             dbQuery = context.BaseItems.AsNoTracking().Where(e => groupedIds.Contains(e.Id));
         }
         else if (filter.GroupBySeriesPresentationUniqueKey)
         {
-            var groupedIds = dbQuery.GroupBy(e => e.SeriesPresentationUniqueKey).Select(e => e.Min(x => x.Id));
+            var groupedIds = candidates
+                .Where(e => !candidates.Any(o => o.SeriesPresentationUniqueKey == e.SeriesPresentationUniqueKey && o.Id.CompareTo(e.Id) < 0))
+                .Select(e => e.Id);
             dbQuery = context.BaseItems.AsNoTracking().Where(e => groupedIds.Contains(e.Id));
         }
         else