fix(swarm): per-slot Mnesia volume via Swarm name template.

Co-authored-by: Cursor <cursoragent@cursor.com>

docker/docker-compose.swarm.yml

@@ -76,10 +76,8 @@ services:
           - eventhub
           - eventhub-node
     volumes:
-      # Per-task volume when scaling replicas > 1 (never share one Mnesia dir).
-      - type: volume
-        source: eventhub-data-{{.Task.Slot}}
-        target: /app/data
+      # Per-task Mnesia via Swarm volume name template when replicas > 1.
+      - eventhub-data:/app/data
     deploy:
       replicas: 1
       endpoint_mode: dnsrr
@@ -227,8 +225,8 @@ networks:
     driver: overlay
 
 volumes:
-  # eventhub-data-{{.Task.Slot}} created by Swarm from service mount template
-  # (do not use a single shared volume for multi-replica Mnesia)
+  eventhub-data:
+    name: 'eventhub-data-{{.Task.Slot}}'
   prometheus-data:
   grafana-data:
   traefik-logs: