Pantry tracking JSON API with tests

Build a small dependency-free Node.js HTTP JSON API that tracks a household pantry. Items have a name, a quantity (non-negative number), a unit (free text such as "g" or "pcs") and an optional expiry date (YYYY-MM-DD). Routes: list items, create an item, update an item's quantity or expiry, delete an item, and a report route that lists items expiring within the next seven days sorted by expiry. Invalid payloads (missing name, negative quantity, malformed date) are refused with a 400 and a JSON error message; an unknown id is a 404. State persists in one JSON file under a data directory so it survives a restart. The server reads PORT from the environment and announces the bound port on stdout. Include executable tests that exercise every route including the error cases and the restart persistence, runnable from a clean checkout with one documented command, and a README with the routes, payloads and how to run. Completion is observable by starting the server, calling each route, restarting it and seeing the data preserved, and by the tests passing.

Continue the existing pantry API from its delivered workspace. Serve a small browser page from the same Node process at the root path: it lists the pantry items in a table (name, quantity, unit, expiry), highlights items expiring within seven days, offers a form to add an item and a button per row to delete it, and shows the API's error message inline when the server refuses a payload. The page uses only the existing routes through fetch, has no external packages, and must stay usable with the keyboard only. Keep every API route and its tests unchanged and passing, and add tests or recorded checks proving that the root path serves the page and that the page's add and delete actions change the data the list route returns. Completion is observable in a real browser against the running server: adding an item shows it in the table and in the list route, deleting removes it from both, and an invalid add shows the server's error inline.