Fix: Downgrade transformers to 4.36.2 for PyTorch 2.1.0 compatibility

Rollback: Revert FastAPI to 0.104.1

Security Phase 1: Update FastAPI from 0.104.1 to 0.109.1

Security: Update transformers from 4.35.0 to 4.53.1

Deploy Visualisable.ai backend with API protection