Revert "chore(deps): update postgres docker tag to v17"

[cte]

Reverts #4350

Annoyingly the db files created by Postgres 15 won't work with Postgres 17 - reverting for now.

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Important

Reverts Postgres Docker image from 17.5 to 15.4 in docker-compose.yml due to db file incompatibility.

• Revert Postgres Version:
  • Reverts Postgres Docker image from 17.5 to 15.4 in docker-compose.yml for db service due to incompatibility with existing db files.

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