feat: rebuild base repository hierarchy, add readme and agents

- replace EfRepository/BaseDbContext/UtcValueConverter with BaseEfRepository and BaseRepository
- add IEfRepository interface hierarchy
- consolidate IEntity into Entity.cs, remove standalone IEntity.cs
- add PagedResult
- adjust all namespaces to HrynCo.DAL.Abstract / HrynCo.DAL.EF
- add README.md with solution overview, versioning rules, class diagram
- add AGENTS.md

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

HrynCo.DAL.EF/Core/EfTransactionAdapter.cs

@@ -1,29 +1,29 @@
+namespace HrynCo.DAL.EF.Core;
+
 using HrynCo.DAL.Abstract;
 using Microsoft.EntityFrameworkCore.Storage;
 
-namespace HrynCo.DAL.EF.Core;
-
-internal sealed class EfTransactionAdapter : ITransaction
+public class EfTransactionAdapter : ITransaction
 {
-    private readonly IDbContextTransaction _transaction;
+    private readonly IDbContextTransaction _efTransaction;
 
-    internal EfTransactionAdapter(IDbContextTransaction transaction)
+    public EfTransactionAdapter(IDbContextTransaction efTransaction)
     {
-        _transaction = transaction;
+        _efTransaction = efTransaction;
     }
 
     public Task CommitAsync(CancellationToken cancellationToken = default)
     {
-        return _transaction.CommitAsync(cancellationToken);
+        return _efTransaction.CommitAsync(cancellationToken);
     }
 
     public Task RollbackAsync(CancellationToken cancellationToken = default)
     {
-        return _transaction.RollbackAsync(cancellationToken);
+        return _efTransaction.RollbackAsync(cancellationToken);
     }
 
     public ValueTask DisposeAsync()
     {
-        return _transaction.DisposeAsync();
+        return _efTransaction.DisposeAsync();
     }
 }