Use Datum service network for API polling

.env.example

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