canbus: point DSI alert at the right Discord webhook

The Gatus webhook delivered to a channel nobody reads; the secret on the
Pi now holds the confirmed server-alerts webhook (URL stays out of the
repo as before).

Co-Authored-By: Claude Fable 5 <[email protected]>

canbus/ha/dsi_fault_alert.yaml

@@ -7,7 +7,8 @@
 # Deploy to Pi: /config/packages/dsi_fault_alert.yaml
 # Repo copy:    canbus/ha/dsi_fault_alert.yaml
 # Secret:       discord_server_alerts_webhook in the Pi's /config/secrets.yaml
-#               (same webhook Gatus uses for the alerts channel)
+#               (NOT the Gatus webhook — that one posts somewhere Wes doesn't
+#               read; this one is confirmed delivering to the alerts channel)
 
 rest_command:
   discord_server_alerts: