Fix Postgres compose volume mount

[cursor]

Summary

• Mount the pgdata named volume at Postgres' actual default data directory (/var/lib/postgresql/data).

Bug and impact

• The compose service declared a persistent pgdata volume but mounted it at /var/lib/postgresql/data2 while the official Postgres image writes database files to /var/lib/postgresql/data by default.
• Recreating the container could discard catalog database contents because the live database directory was stored in the container filesystem instead of the named volume.

Root cause

• The volume path was changed away from Postgres' default PGDATA location without also setting PGDATA to match.

Fix and validation

• Updated docker-compose.yml to mount pgdata at /var/lib/postgresql/data.
• Validation: committed and pushed the change; verified the file contains the expected mount and no stale /data2 mount remains.
• Note: docker compose config could not be run in this environment because Docker is not installed (docker: command not found).