feat(templates): add localized push templates and actions

Share template keys across email and push with independent editors and revisions. Render localized actions and preserve version-one delivery.

Ref: IT-1627

HrynCo.NotificationService.Web/Views/AdminPushTemplates/Missing.cshtml

@@ -0,0 +1,23 @@
+@using HrynCo.NotificationService.Web.Controllers.Admin.ViewModels
+@model TemplateChannelNavigationViewModel
+@{
+    Layout = "~/Views/Shared/_EditorLayout.cshtml";
+    ViewData["Title"] = "Template: " + Model.Key;
+    ViewData["EditorTitle"] = ViewData["Title"];
+    var channel = Model.IsPush ? "Push" : "Email";
+}
+@section Breadcrumbs {
+<nav aria-label="Breadcrumb" class="template-editor-breadcrumbs"><ol class="breadcrumb"><li class="breadcrumb-item"><a href="/admin/services">Services</a></li><li class="breadcrumb-item"><a href="/admin/services/@Model.ServiceId">@Model.ServiceName</a></li><li class="breadcrumb-item active" aria-current="page">Template</li></ol></nav>
+}
+<dl class="template-service-context"><dt>Service</dt><dd>@Model.ServiceName</dd><dt>Template Key</dt><dd>@Model.Key</dd></dl>
+<partial name="_TemplateChannelNavigation" model="Model" />
+<div class="empty-state"><p>@channel template has not been created for this key.</p>
+@if (Model.IsPush) {
+    <a class="btn btn-primary" asp-action="Create" asp-route-serviceId="@Model.ServiceId" asp-route-key="@Model.Key" asp-route-keyFilter="@Model.KeyFilter">Create Push Template</a>
+} else {
+    <a class="btn btn-primary" asp-action="Create" asp-controller="AdminTemplates" asp-route-serviceId="@Model.ServiceId" asp-route-templateKey="@Model.Key" asp-route-keyFilter="@Model.KeyFilter">Create Email Template</a>
+}
+</div>
+@section FormActions {
+    <a href="@Url.Action("Index", "AdminTemplates", new { serviceId = Model.ServiceId, key = Model.KeyFilter })" class="btn btn-secondary">Back to Templates</a>
+}