feat(ec2): add EC2 Instance resource with code bundling

[sam-goodwin]

Summary

• Add EC2 Instance resources following the Lambda pattern for code bundling and deployment
• Instance accepts a callback handler that gets bundled via esbuild and deployed to run on the instance
• Automatic IAM role + instance profile creation with ec2.amazonaws.com trust policy
• User data script bootstraps Amazon Linux 2023 with Node.js and systemd service management
• Hybrid update strategy: code changes via SSM Run Command, infrastructure changes via replacement

New Files

File	Purpose
instance.ts	Instance Runtime definition and types (props, attrs, bindings)
instance.provider.ts	Full provider implementation with lifecycle management
instance.process.ts	Long-running process helper for background workers
instance.serve.ts	HTTP server helper for web applications
instance.handler.ts	Runtime utilities (toHandler, loadEnv, onShutdown)

Key Features

• Same binding pattern as Lambda - env vars + IAM policy statements
• Code bundling - Uses existing esbuild infrastructure
• S3 storage - Code uploaded to alchemy assets bucket
• SSM integration - Code updates deployed without instance replacement
• systemd service - Process management with auto-restart

Test plan

• Deploy a simple Instance.process worker
• Deploy an Instance.serve HTTP server
• Verify code updates via SSM work correctly
• Verify instance termination cleans up all IAM resources
• Verify bindings (S3, SQS, DynamoDB) work correctly

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