chore(deps): update postgres:18 docker digest to a688ae5

Author: renovate[bot]

.github/workflows/ci-pipeline.yml

@@ -142,7 +142,7 @@ jobs:
 
     services:
       postgres:
-        image: postgres:18@sha256:38d5c9d522037d8bf0864c9068e4df2f8a60127c6489ab06f98fdeda535560f9
+        image: postgres:18@sha256:a688ae5c99f86c1424e046ace0de890608cc0ddb5ec8ef72a6ff8305fdc8f4d2
         env:
           POSTGRES_PASSWORD: testpass
           POSTGRES_DB: testdb