feat: wire up Program.cs, DI extensions, Serilog, and appsettings

- ServiceCollectionExtensions in DAL.EF: AddNotificationDataAccess (DbContext, UoW, repositories)
- ServiceCollectionExtensions in Services: AddNotificationServices (MediatR + TransactionBehavior)
- Api/Program.cs: Serilog, OpenAPI, controllers, DI wiring
- Worker/Program.cs: Serilog, DI wiring
- appsettings.json: Serilog config with Console + Seq sinks, connection string
- appsettings.Development.json: Debug log level overrides

Ref: IT-628

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

HrynCo.NotificationService.Worker/Program.cs

@@ -1,7 +1,19 @@
+using HrynCo.NotificationService.DAL.EF;
+using HrynCo.NotificationService.Services;
 using HrynCo.NotificationService.Worker;
+using Serilog;
 
 var builder = Host.CreateApplicationBuilder(args);
+
+builder.Services.AddSerilog(lc =>
+    lc.ReadFrom.Configuration(builder.Configuration));
+
+string connectionString = builder.Configuration.GetConnectionString("Default")
+    ?? throw new InvalidOperationException("Connection string 'Default' is not configured.");
+
+builder.Services.AddNotificationDataAccess(connectionString);
+builder.Services.AddNotificationServices();
 builder.Services.AddHostedService<Worker>();
 
 var host = builder.Build();
-host.Run();
+host.Run();