build(deps): bump docker/build-push-action from 6.1.0 to 6.18.0

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 6.1.0 to 6.18.0.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v6.1.0...v6.18.0)

---
updated-dependencies:
- dependency-name: docker/build-push-action
  dependency-version: 6.18.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/docker.yml

@@ -35,7 +35,7 @@ jobs:
           registry: registry.opencode.de
           username: access-token
           password: ${{ secrets.OPENCODE_DOCKER_ACCESS_TOKEN }}
-      - uses: docker/build-push-action@v6.1.0
+      - uses: docker/build-push-action@v6.18.0
         with:
           context: .
           push: true