Add genre feature; extract ConfirmModal for reusable confirm dialogs

Genres seed on boot, are editable per project, and gate agent config
errors more gracefully. ConfirmModal replaces ad-hoc confirm prompts
across chapters, tags, and characters pages.

src/Novelly.Api/Genres/Genre.cs

@@ -0,0 +1,8 @@
+namespace Novelly.Api.Genres;
+
+public class Genre
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+
+    public string Name { get; set; } = string.Empty;
+}