feat: repair matcher candidates through redis projection

server/store/redis_candidates.go

@@ -49,6 +49,15 @@ func (p CandidateProjection) Snapshot(ctx context.Context, now time.Time) ([]dom
 	}
 	candidates, err := p.Index.Snapshot(ctx, now)
 	if err == nil {
+		// An empty index is indistinguishable from a Redis restart or a lost
+		// keyspace. Rebuild from PostgreSQL before returning so queued players
+		// are not hidden until the next enqueue mutation.
+		if len(candidates) == 0 {
+			if err := p.Repair(ctx, now); err != nil {
+				return nil, err
+			}
+			return p.Index.Snapshot(ctx, now)
+		}
 		return candidates, nil
 	}
 	if err := p.Repair(ctx, now); err != nil {