chore: explicitly specify -f Containerfile in workflow

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Jonathan D.A. Jewell

.github/workflows/ghcr-publish.yml

@@ -49,7 +49,7 @@ jobs:
 
       - name: Build image
         run: |
-          sudo nerdctl build -t ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }} .
+          sudo nerdctl build -f Containerfile -t ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }} .
           sudo nerdctl tag ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }} ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
 
       - name: Push image