refactor: rename Api project to Web

- HrynCo.NotificationService.Api -> HrynCo.NotificationService.Web
- HrynCo.NotificationService.Api.IntegrationTests -> HrynCo.NotificationService.Web.IntegrationTests
- Updated slnx, docker-compose, project references, and namespaces
- Project serves both REST API and admin UI

Ref: IT-628

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

docker/environments/docker-compose.yml

@@ -2,7 +2,7 @@ services:
   api:
     build:
       context: ../..
-      dockerfile: HrynCo.NotificationService.Api/Dockerfile
+      dockerfile: HrynCo.NotificationService.Web/Dockerfile
     environment:
       - ASPNETCORE_ENVIRONMENT=Production
       - App__ConnectionString=${CONNECTION_STRING}