chore(deps): update postgres:18.6-alpine docker digest to 898c60c (#323)

k8s/infra/postgres.yaml

@@ -53,7 +53,7 @@ spec:
     spec:
       containers:
       - name: postgres
-        image: postgres:18.6-alpine@sha256:83148c0bc09eac4d598b70a61e1404d0212b76c95c504bfd6c81a4c59ec91792
+        image: postgres:18.6-alpine@sha256:898c60cb390d1085bc97bdd6a1ae968757421df394b071848b52b1c09c89d6a5
         args:
         - -c
         - shared_buffers=384MB