feat(systemd): Autoamtically fall back to container image

This patch makes the systemd unit automatically fall back to
the podman container in order to run hcloud-dynfw. This reduces
the friction to get things set up.

systemd/wrapper.sh

 #!/bin/sh
 
+XDG_CONFIG_HOME="${XDG_CONFIG_HOME:-$HOME/.config}"
+
 # Allow to load the secret from proper secrets store
 # in this key GNOME keyring
 if [ -z "$HCLOUD_TOKEN" ]; then
   export HCLOUD_TOKEN="$(secret-tool lookup com.shivering-isles.git.sheogorath.hcloud-dynfw/api.hetzner.cloud api-key)"
 fi
 
+if command -v hcloud-dynfw >/dev/null 2>&1; then
   exec hcloud-dynfw
+else
+  podman run --rm -it -e HCLOUD_TOKEN --env-file "$XDG_CONFIG_HOME/hcloud-dynfw/env" quay.io/sheogorath/hcloud-dynfw
+fi