feat(templates): add service language template management

Add normalized service and template catalogs, scoped administration, migration, validation, and regression coverage.

Ref: IT-1601

HrynCo.NotificationService.Web.IntegrationTests/TemplateWebApplicationFactory.cs

@@ -0,0 +1,13 @@
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class TemplateWebApplicationFactory(string connectionString) : WebApplicationFactory<Program>
+{
+    protected override void ConfigureWebHost(IWebHostBuilder builder)
+    {
+        builder.UseEnvironment("Testing");
+        builder.UseSetting("App:ConnectionString", connectionString);
+    }
+}