refactor: update skeleton and scripts

skel/opt/scripts/restic/backup.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+ntfy() {
+    sh /opt/scripts/ntfy.sh -s "/neb/secrets/ntfy/ixvd-backups" -u "https://push.ixvd.net/ixvd-backups" "$@"
+}
+
+ntfy -m "performing backup..."
+if restic \
+    -r "sftp://ixvd_backup_storage//$(hostname)" \
+    -p "/neb/secrets/restic/$(hostname).secret" \
+    backup \
+    --tag auto \
+    /srv /home /etc; then
+    ntfy -m "backup succeeded"
+else
+    ntfy -m "backup failed" -e "warning,skull"
+fi