fix: correct notification template filter links

Use explicit Razor interpolation for create and edit URLs and cover the rendered link syntax with a regression test.

Ref: IT-1039

HrynCo.NotificationService.Web.IntegrationTests/AdminTemplatesIndexViewTests.cs

@@ -0,0 +1,32 @@
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminTemplatesIndexViewTests
+{
+    [Fact]
+    public void CreateAndEditLinks_UseExplicitFilterQueryInterpolation()
+    {
+        string view = File.ReadAllText(FindIndexView());
+
+        Assert.Contains("/admin/templates/create@(filterQuery)", view);
+        Assert.Contains("@t.LanguageCode@(filterQuery)", view);
+        Assert.DoesNotContain("create@filterQuery", view);
+        Assert.DoesNotContain("LanguageCode@filterQuery", view);
+    }
+
+    private static string FindIndexView()
+    {
+        DirectoryInfo? directory = new(AppContext.BaseDirectory);
+        while (directory is not null && !File.Exists(Path.Combine(directory.FullName, "HrynCo.NotificationService.slnx")))
+        {
+            directory = directory.Parent;
+        }
+
+        Assert.NotNull(directory);
+        return Path.Combine(
+            directory.FullName,
+            "HrynCo.NotificationService.Web",
+            "Views",
+            "AdminTemplates",
+            "Index.cshtml");
+    }
+}