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/Views/AdminServices/DeleteService.cshtml

@@ -0,0 +1,24 @@
+@using HrynCo.NotificationService.Web.Controllers.Admin.ViewModels
+@model NotificationServiceDeleteViewModel
+@{ ViewData["Title"] = "Delete service"; }
+<div class="admin-delete-confirmation">
+<nav aria-label="Breadcrumb"><ol class="breadcrumb"><li class="breadcrumb-item"><a href="/admin/services">Services</a></li><li class="breadcrumb-item active" aria-current="page">Delete service</li></ol></nav>
+<h2>Delete service @Model.Name?</h2>
+<div asp-validation-summary="All" class="text-danger" role="alert"></div>
+@if (Model.DefinitionCount > 0)
+{
+    <div class="alert alert-warning">This service still has <strong>@Model.DefinitionCount template definition(s)</strong>, including definitions without translations. Remove every definition before deleting the service.</div>
+    <a href="/admin/services/@Model.ServiceId" class="btn btn-primary mb-3">View templates</a>
+}
+else
+{
+    <div class="alert alert-danger">This permanently deletes the service and its language catalog.</div>
+}
+<p>Email channels are retained. Their service names are independent and are not renamed or deleted.</p>
+<form asp-action="DeleteService" asp-route-serviceId="@Model.ServiceId" method="post">
+    @Html.AntiForgeryToken()
+    <input asp-for="Revision" type="hidden" />
+    <div class="form-check mb-3"><input asp-for="ConfirmDelete" class="form-check-input" disabled="@(Model.DefinitionCount > 0)" /><label asp-for="ConfirmDelete" class="form-check-label">I confirm deletion of service @Model.Name and its language catalog.</label></div>
+    <div class="d-flex flex-wrap gap-2"><button type="submit" class="btn btn-danger" disabled="@(Model.DefinitionCount > 0)">Delete service</button><a class="btn btn-secondary" href="/admin/services">Cancel</a></div>
+</form>
+</div>