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/files/cloud_init_global.tpl

@@ -8,3 +8,8 @@ resolv_conf:
 
 preserve_hostname: false
 fqdn: ${hostname}.${domain}
+
+users:
+  - name: micqdf
+    ssh_authorized_keys:
+      - ${SSH_KEY_PUBLIC}