feat: add terraform generate command to export workspace resources to HCL (#25)
Adds `openstatus terraform generate` (alias `tf gen`) that fetches all workspace resources and generates Terraform HCL files with import blocks. - New `internal/terraform/` package with fetch, HCL generation (hclwrite), naming/dedup, region mapping (28 regions), and enum converters - Generates provider.tf, monitors.tf, notifications.tf, status_pages.tf, and imports.tf in ./openstatus-terraform/ - Supports HTTP, TCP, DNS monitors, 12 notification providers, status pages with components and component groups - Cross-references single-value fields (page_id, monitor_id, group_id) as Terraform traversals with fallback to raw strings - Sensitive values emitted as "REPLACE_ME" with TODO comments - Updates CLI skill with terraform trigger phrases and workflow docs