#613 f-string in logging: 528 remaining occurrences across codebase

Top files: activity_worker.py(35), platform.py(25), http_request.py(20), llm.py(16), docker/network.py(16), secret_providers.py(16), docker/container.py(15), shell_output_streamer.py(14), datashard_logger.py(14), s3_provider.py(14). Need systematic fix.