feat: add destroy subcommand to tear down deployed servers

[dguido]

Summary

• Add ./algo destroy <server-ip> subcommand to programmatically remove cloud resources and clean up local configs
• Create destroy.yml playbook that loads server config, gathers provider credentials, confirms with user, and dispatches to provider-specific destroy tasks
• Add destroy task files for all 11 cloud providers (DigitalOcean, EC2, Lightsail, Azure, GCE, Hetzner, Vultr, Scaleway, OpenStack, CloudStack, Linode)
• Store algo_region in .config.yml during deployment so destroy can auto-detect region
• Fix Scaleway custom module to use required_if instead of unconditional required=True for image, commercial_type, organization — enables state: absent without placeholder values
• Add Vultr to region-required providers and store algo_region in Vultr prompts

Details

The destroy flow:

1. Validates server_ip is provided
2. Loads configs/<ip>/.config.yml to get provider, server name, and region
3. Installs cloud provider dependencies
4. Gathers credentials via existing prompts.yml files (no duplicated auth logic)
5. Displays destroy plan and confirms with user (skip with -e confirm_destroy=true)
6. Dispatches to roles/cloud-<provider>/tasks/destroy.yml
7. Removes local config directory and localhost symlink if applicable

Provider-specific behavior:

• EC2/Lightsail: Delete CloudFormation stack (cascading resource cleanup)
• Azure: Delete entire resource group with force_delete_nonempty
• GCE: Delete instance + best-effort cleanup of firewall, static IP, network
• Vultr/OpenStack/CloudStack: Delete instance + best-effort cleanup of firewall/security groups
• Others: Instance deletion only
• Local: Config cleanup only (no cloud resources)

Region handling: EC2, Lightsail, GCE, Scaleway, and Vultr require region for deletion. The region is auto-detected from .config.yml for new deployments. For servers deployed before this change, pass -e region=YOUR_REGION.

Test plan

• ansible-playbook destroy.yml --syntax-check passes
• ansible-lint destroy.yml passes at production profile
• pytest tests/unit/test_destroy.py -q — 22 tests pass
• pytest tests/unit/ -q — full suite (119 tests) passes
• ./algo destroy shows usage and exits 1
• ./algo help lists destroy command
• All pre-commit hooks pass (yamllint, shellcheck, ruff, semgrep, ansible-lint)

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