dch-proxy: Proxy Victoria Metrics

Need to expose Victoria Metrics to the Internet so the `vmagent` process
on the VPS can push the metrics it has scraped from its Blackbox
exporter.  Authelia needs to allow access to the `/insert/` paths, of
course.

group_vars/dch-proxy.yml

@@ -60,6 +60,8 @@ dch_proxy_sites:
   match: invoiceninja.pyrocufflink.net
 - backend: kubernetes
   match: dynk8s-provisioner.pyrocufflink.net
+- backend: kubernetes
+  match: metrics.pyrocufflink.blue
 
 dch_proxy_backends:
   bitwarden: