System architecture.

public class CvManager : ICvService
{
    ICvDAL _DLL;

    public CvManager(ICvDAL dLL)
    {
        _DLL = dLL;
    }

    public List<Cv> ReadAll() => _DLL.ReadAll();
    public Cv ReadById(int t) => _DLL.ReadById(t);
    public void Create(Cv t) => _DLL.Create(t);
    public void Update(Cv t) => _DLL.Update(t);
    public void Delate(Cv t) => _DLL.Delate(t);
}

public class GenericRepository<T> : IGenericDAL<T> where T : class
{
    private readonly AddDbContext _context;

    public GenericRepository(AddDbContext context)
    {
        _context = context;
    }

    public void Create(T t)
    {
        _context.Add(t);
        _context.SaveChanges();
    }

    public List<T> ReadAll() => _context.Set<T>().ToList();

    public T ReadById(int id) => _context.Set<T>().Find(id);

    public void Update(T t)
    {
        _context.Update(t);
        _context.SaveChanges();
    }
}

public class AddDbContext : IdentityDbContext<User, Roll, int>
{
    public AddDbContext(DbContextOptions<AddDbContext> options,
                         IHttpContextAccessor? httpContextAccessor = null)
        : base(options)
    {
        _httpContextAccessor = httpContextAccessor;
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        // Viele-zu-viele zwischen ProjectDetail und Technicalskills
        modelBuilder.Entity<ProjectDetail>()
            .HasMany(pd => pd.TechStack)
            .WithMany(t => t.projectDetails);
    }

    public DbSet<Project> projects { get; set; }
    public DbSet<Cv> cvs { get; set; }
    // … 19 weitere DbSets, ein Set pro Entity
}

builder.Services.AddDbContext<AddDbContext>(options =>
{
    options.UseSqlite($"Data Source={dbPath}");
});

builder.Services.AddIdentity<User, Roll>(options =>
{
    options.Password.RequireDigit = false;
    options.Password.RequiredLength = 4;
})
.AddEntityFrameworkStores<AddDbContext>()
.AddDefaultTokenProviders();

// Eine generische Registrierung deckt GenericRepository<T>
// für ALLE Entities gleichzeitig ab:
builder.Services.AddScoped(typeof(IGenericDAL<>), typeof(GenericRepository<>));

builder.Services.AddScoped<ICvDAL, EfCvDAL>();
builder.Services.AddScoped<CvManager>();