Add blinker==1.4 to requirements.txt so that HuggingFace Inference Endpoint does not try to uninstall it - which it fails to do

chore: split the dependencies over two files: requirements.txt (used by HF Inference Endpoint) and requirements_extra.txt (only for local development) . Goal is to prevent the error 'Cannot uninstall 'blinker' seen in the HF Inference Endpoint logs

Add environment for local development and testing