refactor: stop using the legacy standalone server

Signed-off-by: Camila Belo <camilaibs@gmail.com>

plugins/app-backend/dev/index.ts

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2024 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { createBackend } from '@backstage/backend-defaults';
+
+const backend = createBackend();
+backend.add(import('../src/alpha'));
+backend.start();