Upgrade fastapi from 0.116.2 -> 0.120.1 (#16)

The upgrade brings in starlette 0.49.1 thus resolving GitHub Dependabot alerts.

poetry.lock was regenerated by running poetry update on a test GCP VM with:
   - Ubuntu 24.04.3 LTS
   - Poetry 1.8.2
   - Python 3.12.3

Tested on the production server.

Author: Elenetta17