multi-controller update

.env.example

@@ -1,6 +1,17 @@
+# Optional seed values for an auto-created "Default" controller.
+# Only used on first boot when no controllers exist yet. After that, manage
+# controllers from the dashboard UI (Controllers button).
 UNIFI_HOST=10.0.0.1
 UNIFI_PORT=12445
 UNIFI_API_TOKEN=YOUR_ACCESS_DEVELOPER_TOKEN_HERE
 WEBHOOK_SECRET=YOUR_WEBHOOK_SECRET_HERE
+
+# Required.
 TZ=America/Chicago
 DB_PATH=/data/dashboard.db
+
+# Optional. Used when registering webhooks on controllers so they know how to
+# reach this dashboard. If unset, the URL is derived from the browser request
+# used to add the controller. Set this if your controller can't reach that URL
+# (e.g. you added the controller from a different network).
+# DASHBOARD_BASE_URL=http://10.0.0.5:8000