manatee: Add schema

The household weekly plan at schema.ppp.pm: its module, certificate,
DNS record, backup and secrets. The link to puppy-tracker is prepared
but commented out until puppy-tracker with the integration feed is
deployed.

hosts/manatee/modules/certs/default.nix

@@ -30,6 +30,7 @@ in
       "romm.ppp.pm"
       "puppy.ppp.pm"
       "todo.ppp.pm"
+      "schema.ppp.pm"
     ] (_: hetznerCert);
   };