chore(deps): update docker.io/postgres docker tag to v18 (#137)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| docker.io/postgres | major | `17.5-alpine3.22` -> `18.0-alpine3.22` |

---

### Configuration

📅 **Schedule**: Branch creation - "on Sunday" (UTC), 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 this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR was generated by [Mend Renovate](https://mend.io/renovate/).
View the [repository job
log](https://developer.mend.io/github/8hobbies/commitrack).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0MS4xNDMuMSIsInVwZGF0ZWRJblZlciI6IjQxLjE0My4xIiwidGFyZ2V0QnJhbmNoIjoibWFzdGVyIiwibGFiZWxzIjpbXX0=-->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

docker-compose.yml

@@ -43,7 +43,7 @@ services:
       - commitrack
 
   db:
-    image: docker.io/postgres:17.5-alpine3.22@sha256:6567bca8d7bc8c82c5922425a0baee57be8402df92bae5eacad5f01ae9544daa
+    image: docker.io/postgres:18.0-alpine3.22@sha256:f898ac406e1a9e05115cc2efcb3c3abb3a92a4c0263f3b6f6aaae354cbb1953a
     container_name: commitrack-db
     ports:
       - "5432:5432"