fix: set alloy container hostname to APEX_NODE_HOST

node_exporter's uname collector reports the container's UTS hostname as
node_uname_info{nodename}, which Docker defaults to the container id. Grafana
surfaces that as the host, so every node showed a hex id instead of its name.
Setting hostname on the alloy service makes nodename the node's public host.
node/instance labels were already correct via the config.alloy relabel.

compositions/apex/docker-compose.yml

@@ -188,6 +188,7 @@ services:
   alloy:
     image: grafana/alloy:v1.17.1
     container_name: apex-alloy
+    hostname: "${APEX_NODE_HOST}"   # UTS hostname => node_exporter's node_uname_info `nodename` (else the container id)
     profiles: [alloy]
     user: "0:0"  # root: required for host metrics, journal, and docker.sock
     volumes: