Mount postgres volumes at /var/lib/postgresql

This is to resolve errors like the following, now that postgres:latest
resolves to the v18 image by default.

```quote
in 18+, these Docker images are configured to store database data in a
format which is compatible with "pg_ctlcluster" (specifically, using
major-version-specific directory names).  This better reflects how
PostgreSQL itself works, and how upgrades are to be performed.

See also docker-library/postgres#1259

Counter to that, there appears to be PostgreSQL data in:
  /var/lib/postgresql/data (unused mount/volume)

This is usually the result of upgrading the Docker image without
upgrading the underlying database using "pg_upgrade" (which requires both
versions).

The suggested container configuration for 18+ is to place a single mount
at /var/lib/postgresql which will then place PostgreSQL data in a
subdirectory, allowing usage of "pg_upgrade --link" without mount point
boundary issues.

See docker-library/postgres#37 for a (long)
discussion around this process, and suggestions for how to do so.
```

Author: mattgallagher92

demos/nodejs-postgres-bucket-storage/docker-compose.yaml

@@ -35,7 +35,7 @@ services:
       - POSTGRES_PASSWORD=${PG_STORAGE_DATABASE_PASSWORD}
       - PGPORT=${PG_STORAGE_DATABASE_PORT}
     volumes:
-      - pg_storage_data:/var/lib/postgresql/data
+      - pg_storage_data:/var/lib/postgresql
     ports:
       - "${PG_STORAGE_DATABASE_PORT}:${PG_STORAGE_DATABASE_PORT}"
     healthcheck:

services/postgres.yaml

@@ -8,7 +8,7 @@ services:
       - POSTGRES_PASSWORD=${PG_DATABASE_PASSWORD}
       - PGPORT=${PG_DATABASE_PORT}
     volumes:
-      - pg_data:/var/lib/postgresql/data
+      - pg_data:/var/lib/postgresql
     ports:
       - "${PG_DATABASE_PORT}:${PG_DATABASE_PORT}"
     command: ["postgres", "-c", "wal_level=logical"]