Fix tmpfs permissions for non-root user in docker-compose.yml

The tmpfs mount at /data defaults to root ownership, but the container
runs as mcpuser (uid 1000). Set uid=1000,gid=1000 on the tmpfs mount
so heap snapshots can be written.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: r33drichards

docker-compose.yml

@@ -15,7 +15,7 @@ services:
       - --session-db-path=/data/sessions
       - --opa-url=http://opa:8181
     tmpfs:
-      - /data
+      - /data:uid=1000,gid=1000
     ports:
       - "3000:3000"
     depends_on: