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/AdminTemplates/Edit.cshtml

@@ -29,13 +29,14 @@
         </div>
         <div class="col-md-6">
             <label asp-for="Key" class="form-label fw-semibold">Template Key</label>
-            <input asp-for="Key" class="form-control" readonly="@(!Model.IsNew)" />
+            <input asp-for="Key" class="form-control" readonly="@(!Model.IsNew || Model.LockKey)" />
         </div>
     </div>
+    <partial name="_TemplateChannelNavigation" model="@(new TemplateChannelNavigationViewModel { ServiceId = Model.ServiceId, Key = Model.Key, KeyFilter = Model.KeyFilter })" />
     <div class="mb-3">
         <label asp-for="VariablesJson" class="form-label fw-semibold">Shared variables (JSON)</label>
         <textarea asp-for="VariablesJson" class="form-control font-monospace" rows="14"></textarea>
-        <div class="form-text">One contract for every language: <code>[{"name":"UserName","required":true}]</code></div>
+        <div class="form-text">Email variables, shared across its languages: <code>[{"name":"UserName","required":true}]</code></div>
     </div>
     <p class="text-muted">Every configured service language has a tab. Present and Missing show saved versions. Leave all three content fields blank for an unused language; clear them to remove an existing version. Shared variables and the template remain.</p>
     @if (Model.Languages.Count == 0) { <p>No service languages configured. You can save the key and shared variables now, then add language codes in Edit Service.</p> }
@@ -102,6 +103,7 @@
     <a id="cancelTemplate" href="@Url.Action("Index", "AdminTemplates", new { serviceId = Model.ServiceId, key = Model.KeyFilter })" class="btn btn-secondary">Cancel</a>
 }
 @section Scripts {
+    <script src="~/js/template-channel-navigation.js" asp-append-version="true"></script>
     <script src="~/js/email-template-preview.js" asp-append-version="true"></script>
     <script src="~/js/email-template-editor.js" asp-append-version="true"></script>
 }