Update package references and modify DbRepository access

- Added conditional package references for AutoMapper in
  `DigitalData.Core.Application.csproj` to support
  different target framework versions.

- Changed `DbRepository` class access modifier from
  `public` to `internal` to encapsulate implementation
  details within the current assembly.

DigitalData.Core.Infrastructure/DbRepository.cs

@@ -5,7 +5,7 @@ using System.Linq.Expressions;
 
 namespace DigitalData.Core.Infrastructure;
 
-public class DbRepository<TDbContext, TEntity> : IRepository<TEntity> where TDbContext : DbContext where TEntity : class
+internal class DbRepository<TDbContext, TEntity> : IRepository<TEntity> where TDbContext : DbContext where TEntity : class
 {
     protected readonly TDbContext Context;