Discover Datum container IP at runtime

.env.example

@@ -13,9 +13,11 @@ LOG_LEVEL=info
 # STATIC_DIR=
 
 # ---- Datum gateway (the Umbrel app we're polling) ----
-# Use Docker DNS on Datum's app network so Datum can be recreated without
-# changing a stale container IP.
-DATUM_URL=http://datum:21000
+# Fallback URL. In Docker deployment, DATUM_DOCKER_* below lets the API discover
+# Datum's current container IP before polling.
+DATUM_URL=http://datum_datum_1:21000
+DATUM_DOCKER_CONTAINER=datum_datum_1
+DATUM_DOCKER_NETWORK=umbrel_main_network
 DATUM_ADMIN_USER=admin
 DATUM_ADMIN_PASSWORD=
 # How often to scrape /clients (ms). Datum updates per-worker hashrate every