The jellyfin-webhook-install oneshot has 'wantedBy = jellyfin.service',
which only runs it when jellyfin (re)starts. On first rollout to a host
where jellyfin is already running, the unit gets added but never fires,
leaving the Webhook plugin files absent -- jellyfin-webhook-configure
then gets 404 from /Plugins/$GUID/Configuration and deploy-rs rolls back.
Pinning jellyfin.restartTriggers to the plugin package + install script
forces a restart whenever either derivation changes, which pulls install
in via the existing before/wantedBy chain.
