Bump docker/metadata-action from 5 to 6

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

---
updated-dependencies:
- dependency-name: docker/metadata-action
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

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

@@ -123,7 +123,7 @@ jobs:
 
       - name: Extract metadata (tags + labels)
         id: meta
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/mediamanager
@@ -204,7 +204,7 @@ jobs:
 
       - name: Extract metadata (tags + labels)
         id: meta
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: |
             ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/mediamanager

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

@@ -88,7 +88,7 @@ jobs:
 
       - name: Extract metadata (tags + labels)
         id: meta
-        uses:  docker/metadata-action@v5
+        uses:  docker/metadata-action@v6
         with:
           images:  |
             ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/metadata_relay
@@ -168,7 +168,7 @@ jobs:
 
       - name: Extract metadata (tags + labels)
         id: meta
-        uses:  docker/metadata-action@v5
+        uses:  docker/metadata-action@v6
         with:
           images:  |
             ghcr.io/${{ github.repository_owner }}/${{ steps.repo_name.outputs.name }}/metadata_relay