Add conditional compilation for .NET Framework support

Updated code to support conditional compilation for .NET Framework and .NET.
Introduced nullable reference types in `DbRepository.cs` and ensured proper initialization of service registration queues in `DependencyInjection.cs`.
Modified `DbRepositoryFactory.cs` and `DbSetFactory.cs` to maintain consistent structure across frameworks.
These changes enhance compatibility and improve type safety.

DigitalData.Core.Infrastructure/Factory/DbSetFactory.cs

@@ -1,6 +1,14 @@
 using Microsoft.EntityFrameworkCore;
+#if NETFRAMEWORK
+using System;
+#endif
 
-namespace DigitalData.Core.Infrastructure.Factory;
+namespace DigitalData.Core.Infrastructure.Factory
+#if NET
+    ;
+#elif NETFRAMEWORK
+    {
+#endif
 
 public class DbSetFactory<TDbContext,TEntity> where TDbContext : DbContext where TEntity : class
 {
@@ -10,4 +18,8 @@ public class DbSetFactory<TDbContext,TEntity> where TDbContext : DbContext where
     {
         Create = create;
     }
-}
+}
+
+#if NETFRAMEWORK
+    }
+#endif