ci: rebuild and push the latest image on schedule

Rebuild and push the last commit of the default branch every monday at 00:00 UTC

.github/workflows/dockerhub.yml

@@ -2,6 +2,8 @@ name: DockerHub
 
 on:
   workflow_dispatch:
+  schedule:
+    - cron: '0 0 * * 1'
   push:
     branches:
       - main