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

policies/transit/decrypt/au-syd1-k8s-vso.hcl

@@ -1,4 +0,0 @@
-# Allow decryption with the au-syd1-k8s-vso key
-path "transit/decrypt/au-syd1-k8s-vso" {
-  capabilities = ["create", "update"]
-}

policies/transit/decrypt/au-syd1-k8s-vso.yaml

@@ -0,0 +1,10 @@
+# Allow decryption with the au-syd1-k8s-vso key
+---
+rules:
+  - path: "transit/decrypt/au-syd1-k8s-vso"
+    capabilities:
+      - create
+      - update
+
+auth: {}
+# Add specific roles here when needed