fixed back routes for stats and added graph component

backend/db/crud.py

backend/main.py

frontend/package-lock.json

frontend/package.json

frontend/src/components/Graph.js

frontend/src/components/WaitingTime.js

frontend/src/components/gradient.js

frontend/src/components/index.js

frontend/src/styles/Footer.css

frontend/src/styles/Graph.css

frontend/src/styles/index.css

frontend/src/views/Eiffel.js