Connect frontend to backend health endpoint

[Homayed]

Set up the frontend foundation and connect it to the FastAPI backend health endpoint.

This issue will create the initial frontend app and display backend health status from the /health endpoint.

Acceptance Criteria:

• Frontend app is created inside frontend/
• Frontend can run locally
• Frontend page calls FastAPI /health
• Page shows loading state while checking backend
• Page shows backend status when connected
• Page shows offline/error state if backend cannot be reached