feat(notification): add admin rest management and deletion

Add revision-safe service and template APIs, channel mapping, and validated admin controls.

Ref: IT-1601

HrynCo.NotificationService.Web/Controllers/Api/Services/DeleteServiceLanguageVersionsRequest.cs

@@ -0,0 +1,13 @@
+using System.Text.Json.Serialization;
+
+namespace HrynCo.NotificationService.Web.Controllers.Api.Services;
+
+public sealed class DeleteServiceLanguageVersionsRequest
+{
+    [JsonRequired]
+    public Guid Revision { get; init; }
+    [JsonRequired]
+    public int ExpectedVersionCount { get; init; }
+    [JsonRequired]
+    public bool ConfirmDelete { get; init; }
+}