chore(deps): bump docker/build-push-action from 5 to 6

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 5 to 6.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v5...v6)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/chart.yaml

@@ -49,14 +49,14 @@ jobs:
         uses: docker/setup-buildx-action@v3
 
       - name: Build backend image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: ./backend/
           load: true
           tags: ghcr.io/${{ github.repository }}/backend:latest
 
       - name: Build frontend image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: ./frontend/
           load: true

.github/workflows/release.yaml

@@ -100,7 +100,7 @@ jobs:
             org.opencontainers.image.licenses=${{ github.event.repository.license.spdx_id }}
 
       - name: Build and Push ${{ matrix.config.name }} Docker Image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         id: docker
         with:
           context: ./${{ matrix.config.name }}/