fix: use repo root as build context for playout to include demodata

.gitea/workflows/ci.yml

@@ -81,7 +81,8 @@ jobs:
       - name: Build and push Playout image
         uses: docker/build-push-action@v5
         with:
-          context: ./backend/playout
+          context: .
+          file: ./backend/playout/Dockerfile
           push: true
           tags: ${{ steps.meta-playout.outputs.tags }}
           labels: ${{ steps.meta-playout.outputs.labels }}