ci: add scheduled build and publish on Tuesdays at 3AM UTC

- Add schedule trigger: weekly on Tuesday at 3:00 AM UTC
- Update publish job condition to run on schedule events (in addition to push)
- Schedule only triggers on main branch (publish job already gated to main)
- build-and-test runs for all triggers; publish only on main push/schedule

Author: KingPin

.github/workflows/docker-ci.yml

@@ -7,6 +7,8 @@ on:
   pull_request:
     branches:
       - '**'
+  schedule:
+    - cron: '0 3 * * 2'  # Weekly on Tuesday at 3:00 AM UTC
   workflow_dispatch:
 
 concurrency:
@@ -216,7 +218,7 @@ jobs:
 
   publish:
     needs: build-and-test
-    if: github.ref == 'refs/heads/main'
+    if: github.ref == 'refs/heads/main' && (github.event_name == 'push' || github.event_name == 'schedule')
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false