update: rotate SSH access via cloud-init secret

Inject SSH public key through Terraform/cloud-init from Gitea secret so access can be rotated without rebuilding the template image.

terraform/variables.tf

@@ -66,3 +66,8 @@ variable "llama_vm_count" {
   default     = 1
   description = "How many Llama VMs to create"
 }
+
+variable "SSH_KEY_PUBLIC" {
+  type        = string
+  description = "Public SSH key injected via cloud-init"
+}