Add food detail route with useEffect + useState

## Goal
Add a food detail route at `/menu/$foodId` that fetches a single food, handles loading, error, and 404 states using the same manual `useEffect` + `useState` pattern.

## Acceptance criteria
- [ ] Route fetches food by id with `useEffect`
- [ ] Loading and error states handled with `useState`
- [ ] Unknown id renders a clear 404 message
- [ ] Detail page shows name, full description, tags, price, image

Start at the `/menu/$foodId` route entry and inspect the existing menu and data-fetching patterns. Done means the route fetches one food by id, shows loading, error, and clear 404 states, and renders its name, full description, tags, price, and image.

Written by the indexing model from the issue text.