Replace deprecated AWS EC2 network_interface blocks

[jimpudar]

Summary

• Switch the generated AWS EC2 Terraform from deprecated network_interface blocks to primary_network_interface
• Attach the firewall’s secondary ENI with aws_network_interface_attachment
• Add explicit Terraform dependencies so the private route and instance state wait for the attachment
• Update the Terraform invariant test to cover the new shape and prevent regressions

Testing

• bun run test
• bun run typecheck
• bun run lint