fix(create-blocks-app): register Amplify auth config

[ikenyal]

Problem

The Amplify Gen 2 overlay adds Cognito values directly to the shared Blocks Lambda environment. This bypasses the shared config registry and consumes the Lambda environment-variable budget. It also injects COGNITO_REGION, which the generated Cognito verifier does not read.

Issue #, if available: N/A

Changes

• Register the generated Cognito verifier's User Pool ID and Client ID through registerConfig() from @aws-blocks/blocks/cdk.
• Remove the unused COGNITO_REGION injection.
• Keep the Amplify Gen 2 integration fixture aligned with the generated overlay.
• Add a scaffold test that verifies the copied overlay uses the config registry and does not directly inject Cognito environment variables.
• 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 (50 passing tests)
• npx tsc --noEmit --target ES2022 --module NodeNext --moduleResolution NodeNext --skipLibCheck test-apps/amplify-gen2/amplify/blocks.ts
• 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: the generated auth API and workflow are unchanged)

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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: a7e7769

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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