fix(prod): bind docker data volume to host /data for persistent disk

Without this override, docker-compose creates a named volume 'agnes_data'
on the boot disk, ignoring any persistent disk mounted at /data by the
VM startup script. This override makes the 'data' volume a bind mount
to host /data, so persistent disks work as expected.

docker-compose.prod.yml

@@ -1,4 +1,7 @@
-# Production override — uses pre-built GHCR image instead of local build.
+# Production override — uses pre-built GHCR image instead of local build,
+# and binds the `data` volume to /data on the host (so persistent-disk mounts
+# at /data are used by all services).
+#
 # Usage: docker compose -f docker-compose.yml -f docker-compose.prod.yml up -d
 # Override tag: AGNES_TAG=stable-2026.04.3 docker compose -f ... up -d
 services:
@@ -16,3 +19,15 @@ services:
     image: ghcr.io/keboola/agnes-the-ai-analyst:${AGNES_TAG:-stable}
   session-collector:
     image: ghcr.io/keboola/agnes-the-ai-analyst:${AGNES_TAG:-stable}
+
+# Override the `data` named volume to bind-mount /data from the host.
+# This ensures a persistent disk mounted at /data (by Terraform startup
+# script) is the actual backing store, not a Docker-managed volume on the
+# boot disk.
+volumes:
+  data:
+    driver: local
+    driver_opts:
+      type: none
+      o: bind
+      device: /data