Move query result classes to QueryOutput namespace

BodyQueryResult and HeaderQueryResult were relocated from ReC.Domain.Entities to ReC.Domain.QueryOutput. Updated all references in IRecDbContext and RecDbContext to use the new namespace.

src/ReC.Domain/QueryOutput/HeaderQueryResult.cs

@@ -0,0 +1,6 @@
+namespace ReC.Domain.QueryOutput;
+
+public class HeaderQueryResult
+{
+    public string? RawHeader { get; init; }
+}