fix: upgrade GitHub Actions to Node.js 24-compatible versions

actions/checkout v3 → v4
docker/login-action pinned SHA → v3
docker/metadata-action pinned SHA → v5
docker/build-push-action pinned SHA → v6

Also skip the push step on pull_request events (was pushing on PRs).
Removes stale env vars username/password that were unused.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Dathan Vance Pattishall

.github/workflows/dockerpublish.yml

@@ -13,12 +13,6 @@ on:
   # Run tests for any PRs.
   pull_request:
 
-env:
-  REGISTRY: ghcr.io
-  IMAGE_NAME: ${{ github.repository }}
-  username: ${{ github.actor }}  # This is your GitHub username automatically
-  password: ${{ secrets.GITHUB_TOKEN }} # No setup required!
-
 permissions:
   contents: read
   packages: write
@@ -30,29 +24,28 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Log in to the Container registry
-        uses: docker/login-action@65b78e6e13532edd9afa3aa52ac7964289d1a9c1
+        uses: docker/login-action@v3
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Extract metadata (tags, labels) for Docker
         id: meta
-        uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
+        uses: docker/metadata-action@v5
         with:
-          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          images: ghcr.io/${{ github.repository }}
           tags: |
             type=ref,event=tag
             type=sha,prefix=commit-
 
-
       - name: Build and push Docker image
-        uses: docker/build-push-action@f2a1d5e99d037542a71f64918e516c093c6f3fc4
+        uses: docker/build-push-action@v6
         with:
           context: .
-          push: true
+          push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}