feat: major restructuring in migration to terragrunt

- 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

config/ssh_secret_backend_role/sshca/signhost.yaml

@@ -0,0 +1,8 @@
+key_type: ca
+algorithm_signer: rsa-sha2-256
+ttl: 315360000  # 87600 * 3600
+allow_host_certificates: true
+allow_user_certificates: false
+allowed_domains: "main.unkin.net,consul"
+allow_subdomains: true
+allow_bare_domains: false