chore(deps): update postgres docker tag to v18

This MR contains the following updates:

Package	Update	Change
postgres	major	17.6 -> 18.0

---

Configuration

📅 Schedule: Branch creation - "after 5pm on monday" in timezone Europe/Paris, Automerge - At any time (no schedule defined).

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

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

🔕 Ignore: Close this MR and you won't be reminded about this update again.

---

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

---

This MR has been generated by Renovate Bot.