Fix manifest job tag reference for tag-push events

`manifest_build_and_push_on_tag` runs on both `push` (tag) and
`release: published`, but referenced `github.event.release.tag_name`
which is only populated for release events. Pushing a tag without
creating a GitHub Release produced an empty value and `docker
manifest create` failed with "invalid reference format" (seen on
the `1.2.2` tag run).

Use `github.ref_name`, which is set for both event types.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: loks0n

.github/workflows/build-and-push.yml

@@ -78,10 +78,10 @@ jobs:
       - name: Create manifest
         run: |
             docker manifest create \
-              ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.event.release.tag_name }} \
+              ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.ref_name }} \
               ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }}-amd64 \
               ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }}-arm64
 
       - name: Push manifest
         run: |
-            docker manifest push ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.event.release.tag_name }}
+            docker manifest push ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.ref_name }}