fix(create-blocks-app): lazy-load React template backend

[ikenyal]

Problem

The React template passes an eagerly imported backend module to createLambdaHandler, but the handler accepts a lazy async factory. This makes the React template inconsistent with every other template and imports the backend before runtime config is loaded.

Issue #, if available: #221

Changes

• Replace the eager backend import in the React template with () => import('./index.js').
• Add a scaffold regression test that verifies the generated React handler uses the lazy factory and does not import the backend eagerly.
• Add a patch changeset for @aws-blocks/create-blocks-app.

Validation

• npm run build --workspace @aws-blocks/create-blocks-app
• npm test --workspace @aws-blocks/create-blocks-app (51 passing tests)
• npm run lint:deps
• changeset status --since=origin/main

Checklist

• PR description included
• Tests are changed or added
• Relevant documentation is changed or added (not applicable: this aligns the generated implementation with the existing documented handler API)

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[changeset-bot]

🦋 Changeset detected

Latest commit: b3a560f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@aws-blocks/create-blocks-app	Patch

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