feat: add AWS Lambda MicroVMs (sandboxes) examples

[czubocha]

What this adds

A three-example gallery for the Serverless Framework sandboxes feature, which deploys AWS Lambda MicroVMs. Each example is self-contained with its own README, serverless.yml, application source, and Dockerfile.

minimal/

The smallest possible configuration: a single sandbox with only the required artifact field. Every other setting falls back to a framework default. Good as a first look at the feature.

complete/

A deploy-as-is showcase of the property surface, exercised by one api sandbox:

• local Dockerfile build, minimumMemory, description, environment
• lifecycle hooks (ready + run)
• full observability — custom metric filters, alarms wired to a self-contained SNS topic, and a dashboard
• custom iam statements merged into the generated least-privilege roles
• tags

VPC egress and a pre-packaged s3:// artifact are included as commented, opt-in blocks (they need account-specific IDs).

self-hosted-webhook/

A webhook control plane that launches one isolated MicroVM per Claude Managed Agents session:

• an API Gateway–fronted launcher Lambda verifies the webhook signature and calls RunMicrovm
• the worker image (built by the sandboxes feature) runs the session
• the README walks through deploying, developing locally against the SDK-compatible emulator, and observing the run via the generated CloudWatch dashboard (screenshots included)

Testing

Each example deploys with serverless deploy and was validated end-to-end: deploy, invoke, log retrieval, and the observability metrics/alarms/dashboard.