chore(deps): update postgres docker tag to v18 (#1103)

| datasource | package  | from | to |
| ---------- | -------- | ---- | -- |
| docker     | postgres | 17   | 18 |

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

Author: renovate[bot]

compose.yaml

@@ -3,7 +3,7 @@ services:
   tux-postgres:
     container_name: tux-postgres
     hostname: tux-postgres
-    image: postgres:17-alpine@sha256:7cd12b4b4bf00307d4ab00e98622290e589e5de767cb55a48b1cf0e71770ae24
+    image: postgres:18-alpine@sha256:eca6fb2d91fda290eb8cfb8ba53dd0dcbf3508a08011e30adb039ea7c8e1e9f2
     restart: 'no'
     environment:
       POSTGRES_DB: ${POSTGRES_DB:-tuxdb}