Update postgres Docker tag to v18

Author: renovate[bot]

compose.yaml

@@ -139,7 +139,7 @@ services:
       - ./test/party-management/sys.config:/opt/party-management/releases/0.1/sys.config
 
   db:
-    image: postgres:15-bookworm
+    image: postgres:18-bookworm
     command: -c 'max_connections=1000'
     environment:
       POSTGRES_MULTIPLE_DATABASES: "hellgate,dmt,party_management,shumway,liminator"