nixos/uptime-kuma: Ensure proper permissions for state directory

Signed-off-by: Felix Singer <[e-mail]>

nixos/modules/services/monitoring/uptime-kuma.nix

···
       serviceConfig = {
         Type = "simple";
         StateDirectory = "uptime-kuma";
+        StateDirectoryMode = "750";
         DynamicUser = true;
         ExecStart = "${cfg.package}/bin/uptime-kuma-server";
         Restart = "on-failure";