[HIGH] require_auth decorator broken - endpoints always return 401

The require_auth decorator checks session['user_id'], but there is no login route, no session creation, and no authentication anywhere. All medicine endpoints guarded by @require_auth will always return 401 - permanently inaccessible.\n\nFile: Backend/routes/medicine.py, lines 14-20\nFix: Remove @require_auth for single-user design, or implement proper auth flow.