feat(07-01): add quick-add HTTP handlers and route registration

- Add ListQuickAddItems, CreateQuickAddItem, UpdateQuickAddItem, DeleteQuickAddItem handler methods
- Register GET/POST /api/quick-add and PUT/DELETE /api/quick-add/{itemId} in authenticated route group
- Validate name non-empty on create and update; return 404 on update when item not found

backend/internal/api/router.go

@@ -70,6 +70,13 @@ func NewRouter(queries *db.Queries, sessionSecret string, frontendFS fs.FS) http
 			r.Delete("/items/{itemId}", h.DeleteTemplateItem)
 		})
 
+		r.Route("/api/quick-add", func(r chi.Router) {
+			r.Get("/", h.ListQuickAddItems)
+			r.Post("/", h.CreateQuickAddItem)
+			r.Put("/{itemId}", h.UpdateQuickAddItem)
+			r.Delete("/{itemId}", h.DeleteQuickAddItem)
+		})
+
 		r.Get("/api/settings", h.GetSettings)
 		r.Put("/api/settings", h.UpdateSettings)
 	})