update monitoring so it works with recent grafana

modules/backup.nix

@@ -15,7 +15,7 @@ in
         type = types.str;
         default = { };
         example = literalExample ''
-          shaarli
+          mossnet
         '';
         description = ''
           name for the backup operator

profiles/monitoring/default.nix

@@ -12,6 +12,9 @@
     locations."/" = {
       proxyPass = "http://127.0.0.1:${toString config.services.grafana.port}";
       proxyWebsockets = true;
+      extraConfig = ''
+        proxy_set_header Host ${config.services.grafana.domain}
+      '';
     };
   };