fix: set build context to root instead of pkg

The build context was set to 'pkg', but the Dockerfile references
requirements.txt and src/ which are at the repository root.
Changing context to '.' gives Docker access to all necessary files.

.gitea/workflows/docker-build.yaml

@@ -39,7 +39,7 @@ jobs:
       - name: Build and push
         uses: docker/build-push-action@v7
         with:
-          context: pkg
+          context: .
           file: pkg/Dockerfile
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}