fix(helm): Correct Postgres volume mount path for persistence

[Darsh-14]

Description

This PR fixes an issue where PySyft datasets and other Postgres data were lost upon cluster reboot or pod restart.

The root cause was that the Postgres StatefulSet in the Helm chart was mounting the persistent volume to tmp/data/db, but the Postgres container writes to /var/lib/postgresql/data by default. This meant data was being written to the container's ephemeral storage instead of the Persistent Volume.

This change updates the mountPath in postgres-statefuleset.yaml to /var/lib/postgresql/data, ensuring data persistence.

Using

• PySyft Helm Chart

Affected Dependencies

None.

How has this been tested?

• Verified the rendered Helm template to ensure the mountPath is correctly set to /var/lib/postgresql/data.
• Standard Postgres usage confirms this is the correct data directory for the official Postgres image.

Checklist

• I have followed the Contribution Guidelines and Code of Conduct
• I have commented my code following the OpenMined Styleguide
• I have labeled this PR with the relevant Type labels
• My changes are covered by tests (verified via configuration inspection)