Massive update

.env.example

@@ -0,0 +1,17 @@
+# Top-level docker-compose environment variables
+# Copy to .env and fill in values before running `docker compose up`
+
+# -----------------------------------------------------------------------
+# MQTT broker credentials
+# These are injected into the mosquitto container at startup to build the
+# password file. Use different values in production — do NOT reuse defaults.
+# -----------------------------------------------------------------------
+
+# C2-core service account (full broker access)
+MQTT_C2_USER=drb-c2-core
+MQTT_C2_PASS=change-me-c2
+
+# Shared credential for all edge nodes (ACL scopes each node to its own
+# nodes/<NODE_ID>/# namespace via the MQTT client ID)
+MQTT_NODE_USER=drb-node
+MQTT_NODE_PASS=change-me-node