Runs tssbot-web, tssbot-webhook, and tssbot-backend as systemd --user
units instead of PM2 processes. tssbot-web moves from a 2-worker PM2
cluster to a single instance, so deploys now restart it directly
instead of doing a zero-downtime cluster reload.
webhook.cjs now shells out to `systemctl --user restart` instead of
`pm2 reload`, and PM2_RESTART_TARGETS/WEBHOOK_PM2_NAME are renamed to
RESTART_TARGETS/WEBHOOK_SERVICE_NAME. scripts/install-systemd-services.sh
symlinks the new unit files into ~/.config/systemd/user and enables them.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Liam