ci: Enable pushing PR builds to GHCR with pr-N tags

.github/workflows/docker.yml

@@ -26,7 +26,6 @@ jobs:
         uses: docker/setup-buildx-action@v3
 
       - name: Log in to Container Registry
-        if: github.event_name != 'pull_request'
         uses: docker/login-action@v3
         with:
           registry: ${{ env.REGISTRY }}
@@ -49,7 +48,7 @@ jobs:
         uses: docker/build-push-action@v6
         with:
           context: .
-          push: ${{ github.event_name != 'pull_request' }}
+          push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha