TM-1: Verify backend API and add tests

[marblehub]

Task:
Clone the repo, run the backend, confirm all API endpoints work, and add or improve at least one backend test.

Files to check:
backend/app/main.py
backend/app/api/
backend/app/models/
backend/tests/

Commands:
cd backend
uv sync
cp ../.env.example .env
uv run pytest
uv run ruff check .

Done when:

• Backend runs locally
• Tests pass
• At least one useful backend test or backend improvement is added
• Pull request is opened into dev

[TaherehHatami]

Hi,
I cloned the repo and installed all packages. All 6 API endpoints are working. All 12 tests passed.
I'll write new backend tests as soon as possible:))

[marblehub]

Alright,
Thanks for the update. Looking forward to the remaining tasks!