feat: replace manual Stopwatch with IProfiler in TransactionBehavior

- Add HrynCo.Common to Services project
- TransactionBehavior now uses IProfiler.MeasureExecutionAsync:
  MeasureExecutionAsync -> ExecuteInTransactionAsync -> next() -> SaveChangesAsync
- Profiler logs Start/End with duration + memory delta via Serilog PerformanceLog context
- Register IProfiler as singleton in ServiceCollectionExtensions (uses Log.Logger)

Ref: IT-628

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

HrynCo.NotificationService.Services/Behaviors/TransactionBehavior.cs

@@ -1,7 +1,6 @@
-using System.Diagnostics;
+using HrynCo.Common;
 using HrynCo.NotificationService.DAL.Abstract;
 using MediatR;
-using Microsoft.Extensions.Logging;
 
 namespace HrynCo.NotificationService.Services.Behaviors;
 
@@ -9,36 +8,21 @@ public class TransactionBehavior<TRequest, TResponse> : IPipelineBehavior<TReque
     where TRequest : notnull
 {
     private readonly IUnitOfWork _unitOfWork;
-    private readonly ILogger<TransactionBehavior<TRequest, TResponse>> _logger;
+    private readonly IProfiler _profiler;
 
-    public TransactionBehavior(IUnitOfWork unitOfWork, ILogger<TransactionBehavior<TRequest, TResponse>> logger)
+    public TransactionBehavior(IUnitOfWork unitOfWork, IProfiler profiler)
     {
         _unitOfWork = unitOfWork;
-        _logger = logger;
+        _profiler = profiler;
     }
 
-    public async Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next, CancellationToken cancellationToken)
-    {
-        string handlerName = typeof(TRequest).Name;
-        _logger.LogDebug("Handling {Handler}", handlerName);
-
-        Stopwatch sw = Stopwatch.StartNew();
-        try
-        {
-            TResponse result = await _unitOfWork.ExecuteInTransactionAsync(async () =>
+    public Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next, CancellationToken cancellationToken) =>
+        _profiler.MeasureExecutionAsync(
+            () => _unitOfWork.ExecuteInTransactionAsync(async () =>
             {
                 TResponse response = await next();
                 await _unitOfWork.SaveChangesAsync(cancellationToken);
                 return response;
-            });
-
-            _logger.LogDebug("Handled {Handler} in {ElapsedMs}ms", handlerName, sw.ElapsedMilliseconds);
-            return result;
-        }
-        catch (Exception ex)
-        {
-            _logger.LogError(ex, "Handler {Handler} failed after {ElapsedMs}ms", handlerName, sw.ElapsedMilliseconds);
-            throw;
-        }
-    }
+            }),
+            typeof(TRequest).Name);
 }