Add missing Postgres image digest in Paperless (#1177)

paperless/docker-compose.yml

@@ -13,7 +13,7 @@ services:
       - ${APP_DATA_DIR}/data/redisdata:/data
 
   db:
-    image: docker.io/library/postgres:16
+    image: docker.io/library/postgres:16@sha256:46aa2ee5d664b275f05d1a963b30fff60fb422b4b594d509765c42db46d48881
     restart: unless-stopped
     volumes:
       - ${APP_DATA_DIR}/data/pgdata:/var/lib/postgresql/data