Rename volume to postgres18-data to avoid v17 data directory conflicts

Agent-Logs-Url: https://github.com/hackclub/hackathons-backend/sessions/eb3d4ab1-0b40-4b20-80fc-db19777bbda6

Co-authored-by: northeastprince <55164724+northeastprince@users.noreply.github.com>

Author: Copilot

docker-compose.yml

@@ -11,7 +11,7 @@ services:
       POSTGRES_DB: hackathons_test
       POSTGRES_HOST_AUTH_METHOD: trust
     volumes:
-      - postgres-data:/var/lib/postgresql/data
+      - postgres18-data:/var/lib/postgresql/data
 
 volumes:
-  postgres-data: {}
+  postgres18-data: {}