feat: add MVC Razor admin UI for email templates

- GetAllEmailTemplatesQuery + handler (new GetAll use case)
- IEmailTemplateRepository.GetAllAsync + EF implementation
- AdminTemplatesController: Index, Create, Edit, Save, Delete
- EmailTemplateEditViewModel with IsNew/PageTitle helpers
- Views/_ViewStart, _ViewImports, Shared/_Layout (Bootstrap 5)
- Shared/_EditorLayout (chained layout for all edit screens)
- Views/AdminTemplates/Index (table with edit/delete actions)
- Views/AdminTemplates/Edit (card form, readonly composite key on edit)
- Program.cs: AddControllersWithViews, UseStaticFiles, MapDefaultControllerRoute

Ref: IT-634

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

HrynCo.NotificationService.Web/Program.cs

@@ -13,7 +13,7 @@ var appSettings = builder.Configuration
 
 builder.Services.AddSingleton(appSettings);
 builder.Services.AddOpenApi();
-builder.Services.AddControllers();
+builder.Services.AddControllersWithViews();
 builder.Services.AddNotificationDataAccess(appSettings.ConnectionString);
 builder.Services.AddNotificationServices();
 
@@ -29,6 +29,8 @@ if (app.Environment.IsDevelopment())
     });
 }
 
+app.UseStaticFiles();
 app.UseHttpsRedirection();
 app.MapControllers();
+app.MapDefaultControllerRoute();
 app.Run();