ci: Adjust Docker build and push conditions

ci: Adjust Docker build and push conditions This change modifies the conditions under which Docker images are built and pushed to Docker Hub. Previously, images were pushed for all events except pull requests. Now, pushes are restricted to the `main` branch, specifically when triggered by a `workflow_run` event originating from the `main` branch, or directly on the `main` branch for other event types. This ensures that only production-ready images are published.