feat(docker): add Docker Hub authentication for CI/CD workflows

- Introduced `docker_hub_token` and `docker_hub_username` secrets for Docker Hub login in CI/CD workflows.
- Updated `.gitea/workflows/ci.yaml`, `.gitea/workflows/cd.yaml`, and `.gitea/workflows/quality.yaml` to utilize these secrets for Docker Hub authentication.
- Enhanced README and releasing documentation to clarify the use of Docker Hub credentials for image mirroring and builds.

.gitea/workflows/ci.yaml

@@ -21,3 +21,5 @@ jobs:
       allow_registry_login: ${{ github.event.pull_request.head.repo.full_name == github.repository }}
     secrets:
       ACTIONS_PAT: ${{ secrets.ACTIONS_PAT }}
+      docker_hub_token: ${{ secrets.docker_hub_token }}
+      docker_hub_username: ${{ secrets.docker_hub_username }}