[ci skip] Add Terragrunt directory skeleton and root config

.gitignore

@@ -45,3 +45,7 @@ modules/kubernetes/frigate/config.yaml
 .claude/._*
 
 ._*
+
+# Terragrunt
+.terragrunt-cache/
+state/

terragrunt.hcl

@@ -0,0 +1,55 @@
+# Root Terragrunt configuration
+# Provides DRY provider, backend, and variable loading for all stacks.
+
+# Each stack gets its own local state file under state/<stack-name>/
+remote_state {
+  backend = "local"
+  generate = {
+    path      = "backend.tf"
+    if_exists = "overwrite_terragrunt"
+  }
+  config = {
+    path = "${get_repo_root()}/state/${path_relative_to_include()}/terraform.tfstate"
+  }
+}
+
+# Load terraform.tfvars for all stacks.
+# Variables not declared by a stack are silently ignored (Terraform 1.x behavior).
+terraform {
+  extra_arguments "common_vars" {
+    commands = get_terraform_commands_that_need_vars()
+    required_var_files = [
+      "${get_repo_root()}/terraform.tfvars"
+    ]
+  }
+
+  extra_arguments "kube_config" {
+    commands = get_terraform_commands_that_need_vars()
+    arguments = [
+      "-var", "kube_config_path=${get_repo_root()}/config"
+    ]
+  }
+}
+
+# Generate kubernetes + helm providers for K8s stacks.
+# The infra stack overrides this to add the proxmox provider.
+generate "k8s_providers" {
+  path      = "providers.tf"
+  if_exists = "overwrite_terragrunt"
+  contents  = <<EOF
+variable "kube_config_path" {
+  type    = string
+  default = "~/.kube/config"
+}
+
+provider "kubernetes" {
+  config_path = var.kube_config_path
+}
+
+provider "helm" {
+  kubernetes {
+    config_path = var.kube_config_path
+  }
+}
+EOF
+}