chore(deps): update postgres docker tag to v18

Author: renovate[bot]

apps/example-better-auth/compose.yaml

@@ -1,6 +1,6 @@
 services:
   db:
-    image: postgres:16.11
+    image: postgres:18.1
     user: postgres
     restart: always
     environment:

apps/example-clerk/compose.yaml

@@ -1,6 +1,6 @@
 services:
   db:
-    image: postgres:16.11
+    image: postgres:18.1
     user: postgres
     restart: always
     environment:

compose.yaml

@@ -1,6 +1,6 @@
 services:
   db:
-    image: postgres:16.11
+    image: postgres:18.1
     user: postgres
     restart: always
     environment: