ci: add workflow to cleanup untagged container packages

Add automated cleanup workflow that runs weekly to remove untagged
container versions from GitHub Container Registry. This helps manage
storage usage and prevents accumulation of intermediate build artifacts
from the build-container.yml and build-ohpc-lint-container.yml workflows.

The workflow includes:
- Weekly scheduled cleanup on Sundays at 2 AM UTC
- Manual trigger with optional dry-run mode for testing
- Cleanup of both main repository and ohpc-lint container images
- Configurable retention policies to keep recent versions

Signed-off-by: Adrian Reber <[email protected]>

Author: adrianreber

.github/workflows/cleanup-packages.yml

@@ -0,0 +1,53 @@
+name: Cleanup Untagged Packages
+
+on:
+  schedule:
+    # Run every Sunday at 02:00 UTC
+    - cron: '0 2 * * 0'
+  workflow_dispatch:
+    inputs:
+      dry_run:
+        description: 'Dry run (preview what would be deleted)'
+        required: false
+        default: 'false'
+        type: boolean
+
+env:
+  REGISTRY: ghcr.io
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Delete untagged container images
+        uses: actions/delete-package-versions@v5
+        with:
+          package-name: ${{ github.repository }}
+          package-type: container
+          min-versions-to-keep: 5
+          delete-only-untagged-versions: true
+          token: ${{ secrets.GITHUB_TOKEN }}
+          dry-run: ${{ github.event.inputs.dry_run == 'true' }}
+
+      - name: Delete old ohpc-lint images
+        uses: actions/delete-package-versions@v5
+        with:
+          package-name: openhpc/ohpc-lint
+          package-type: container
+          min-versions-to-keep: 3
+          delete-only-untagged-versions: true
+          token: ${{ secrets.GITHUB_TOKEN }}
+          dry-run: ${{ github.event.inputs.dry_run == 'true' }}
+
+      - name: Delete old package versions (keep recent tagged)
+        uses: actions/delete-package-versions@v5
+        with:
+          package-name: ${{ github.repository }}
+          package-type: container
+          min-versions-to-keep: 10
+          oldest-to-delete: 30 # Delete versions older than 30 days
+          token: ${{ secrets.GITHUB_TOKEN }}
+          dry-run: ${{ github.event.inputs.dry_run == 'true' }}