Addresses review: a policy's directory should be the base of the paths it
grants, so a code owner of one policy path cannot grant themselves access
elsewhere (e.g. sys or approle).
- policies/rancher/admin.yaml now grants only rancher/{config,service-accounts,
roles}.
- Move the sudo-protected plugin-catalog grant to
policies/sys/plugins/catalog/rancher.yaml (base path sys/plugins/catalog/),
owned by a sys code owner.
- migrate from individual terraform files to config-driven terragrunt module structure
- add vault_cluster module with config discovery system
- replace individual .tf files with centralized config.hcl
- restructure auth and secret backends as configurable modules
- move auth roles and secret backends to yaml-based configuration
- convert policies from .hcl to .yaml format, add rules/auth definition
- add pre-commit hooks for yaml formatting and file cleanup
- add terragrunt cache to gitignore
- update makefile with terragrunt commands and format target