feat: initial solution with HrynCo.DAL.Abstract and HrynCo.DAL.EF

- HrynCo.DAL.Abstract: IEntity<TId>, Entity base classes, ITransaction, IUnitOfWork
- HrynCo.DAL.EF: EfRepository<TDbContext,TEntity>, EfUnitOfWork<TDbContext>, EfTransactionAdapter
- Directory.Packages.props with centralized EF Core 9.0.5 versions
- TeamCity pipeline YAMLs for general-checks and publish

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

HrynCo.DAL.Abstract/IUnitOfWork.cs

@@ -0,0 +1,11 @@
+namespace HrynCo.DAL.Abstract;
+
+public interface IUnitOfWork
+{
+    Task SaveChangesAsync(CancellationToken cancellationToken = default);
+    Task<ITransaction> BeginTransactionAsync(CancellationToken cancellationToken = default);
+    ITransaction? GetCurrentTransaction();
+
+    Task ExecuteInTransactionAsync(Func<Task> action);
+    Task<TResult> ExecuteInTransactionAsync<TResult>(Func<Task<TResult>> action);
+}