chore(deps): update postgres docker tag to v18

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
postgres	service	major	12.22 → 18.3
postgres		major	16 → 18

---

Configuration

📅 Schedule: Branch creation - "every weekend" in timezone US/Eastern, Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about these updates again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.

[github-actions]

OpenAPI Changes

Show/hide No detectable change.

Unexpected changes? Ensure your branch is up-to-date with main (consider rebasing).

[sentry]

Bug: Upgrading the PostgreSQL version will break local development for users with existing data volumes, as the new version cannot read the old data directory format.
_{Severity: HIGH}

Suggested Fix

Provide a data migration path for developers. This could involve documenting the need to manually delete the pgdata volume (docker volume rm <volume_name>) for a fresh start. Alternatively, provide scripts using pg_dump and pg_restore to migrate data from the old version to the new one. The PR should include this guidance in the description or a README file.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: .github/workflows/ci.yml#L11

Potential issue: The pull request upgrades the PostgreSQL Docker image from version 16
to 18. However, the local development environment uses a persistent named volume,
`pgdata`, for the database. When a developer who has previously run the application with
PostgreSQL 16 pulls this change and runs `docker-compose up`, the PostgreSQL 18
container will fail to start. This is because it will detect an incompatible data
directory format from the older version, resulting in a fatal error and breaking the
local development setup. The change does not include any data migration scripts or
documentation for developers to handle this upgrade.