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/appsettings.Development.json

@@ -1,8 +1,12 @@
 {
-  "Logging": {
-    "LogLevel": {
-      "Default": "Information",
-      "Microsoft.Hosting.Lifetime": "Information"
+  "Serilog": {
+    "MinimumLevel": {
+      "Default": "Debug",
+      "Override": {
+        "Microsoft": "Information",
+        "Microsoft.EntityFrameworkCore": "Information",
+        "Microsoft.AspNetCore": "Information"
+      }
     }
   }
-}
+}