chore(deps): update docker.io/library/postgres docker tag to v18

| datasource | package                    | from | to |
| ---------- | -------------------------- | ---- | -- |
| docker     | docker.io/library/postgres | 16   | 18 |

Author: renovate[bot]

mx1/containers/stalwart/docker-compose.yml

@@ -1,7 +1,7 @@
 ---
 services:
   postgres:
-    image: docker.io/library/postgres:16-alpine
+    image: docker.io/library/postgres:18-alpine@sha256:88f300be8635fe8a9ed4c18a68ba497fb6df1215fd2b074895afd027bd3e1006
     restart: unless-stopped
     labels:
       - "com.centurylinklabs.watchtower.enable=true"

web1/containers/authentik/docker-compose.yml

@@ -1,7 +1,7 @@
 ---
 services:
   database:
-    image: docker.io/library/postgres:16-alpine
+    image: docker.io/library/postgres:18-alpine@sha256:88f300be8635fe8a9ed4c18a68ba497fb6df1215fd2b074895afd027bd3e1006
     restart: unless-stopped
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -d $${POSTGRES_DB} -U $${POSTGRES_USER}"]

web3/containers/authentik/docker-compose.yml

@@ -1,7 +1,7 @@
 ---
 services:
   database:
-    image: docker.io/library/postgres:16-alpine
+    image: docker.io/library/postgres:18-alpine@sha256:88f300be8635fe8a9ed4c18a68ba497fb6df1215fd2b074895afd027bd3e1006
     restart: unless-stopped
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -d $${POSTGRES_DB} -U $${POSTGRES_USER}"]

web8/containers/authentik/docker-compose.yml

@@ -1,7 +1,7 @@
 ---
 services:
   postgresql:
-    image: docker.io/library/postgres:16-alpine
+    image: docker.io/library/postgres:18-alpine@sha256:88f300be8635fe8a9ed4c18a68ba497fb6df1215fd2b074895afd027bd3e1006
     restart: unless-stopped
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -d $${POSTGRES_DB} -U $${POSTGRES_USER}"]

web8/containers/stalwart/docker-compose.yml

@@ -1,7 +1,7 @@
 ---
 services:
   postgres:
-    image: docker.io/library/postgres:16-alpine
+    image: docker.io/library/postgres:18-alpine@sha256:88f300be8635fe8a9ed4c18a68ba497fb6df1215fd2b074895afd027bd3e1006
     restart: unless-stopped
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -d $${POSTGRES_DB} -U $${POSTGRES_USER}"]